40,000

Selected numbers in the range 40001–49999

40001 to 40999

• 40320 = smallest factorial (8!) that is not a highly composite number
• 40425 = square pyramidal number
• 40585 = largest factorion
• 40678 = pentagonal pyramidal number
• 40755 = the smallest number 1 to be a Triangular number, Pentagonal number, and a Hexagonal number. Additionally, it's a 390-gonal, 4077-gonal, and 13586-gonal number.
• 40804 = palindromic square

41000 to 41999

• 41041 = Carmichael number
• 41472 = 3-smooth number, number of reduced trees with 24 nodes
• 41586 = Large Schröder number
• 41616 = triangular square number
• 41835 = Motzkin number
• 41841 = 1/41841 = 0.0000239 is a repeating decimal with period 7

42000 to 42999

• 42680 = octahedral number
• 42875 = 353
• 42925 = square pyramidal number

43000 to 43999

• 43261 = Markov number
• 43380 = number of nets of a dodecahedron
• 43390 = number of primes \leq 2^{19}.
• 43560 = pentagonal pyramidal number
• 43691 = Wagstaff prime
• 43777 = smallest member of a prime sextuplet

44000 to 44999

• 44044 = palindrome of 79 after 6 iterations of the "reverse and add" iterative process
• 44100 = sum of the cubes of the first 20 positive integers 44,100 Hz is a common sampling frequency in digital audio (and is the standard for compact discs).
• 44444 = repdigit
• 44583 = number of partitions of 41
• 44721 = smallest positive integer such that the expression − ≤ 10−9
• 44724 = maximum number of days in which a human being has been verified to live (Jeanne Calment).
• 44944 = palindromic square

45000 to 45999

• 45360 = 26th highly composite number; smallest number with exactly 100 factors (including one and itself)

46000 to 46999

• 46080 = double factorial of 12
• 46233 = sum of the first eight factorials
• 46249 = 2nd number that can be written as a^2+b! in 3 ways
• 46368 = Fibonacci number
• 46656 = 216 = 36 = 66, 3-smooth number
• 46657 = Carmichael number
• 46972 = number of prime knots with 14 crossings

47000 to 47999

• 47058 = primary pseudoperfect number
• 47160 = 10-th derivative of xx at x=1
• 47321/33461 ≈ √2

48000 to 48999

• 48629 = number of trees with 17 unlabeled nodes
• 48734 = number of 22-bead necklaces (turning over is allowed) where complements are equivalent

49000 to 49999

• 49151 = Woodall number
• 49152 = 3-smooth number
• 49726 = pentagonal pyramidal number
• 49940 = number of 21-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed

Primes

There are 930 prime numbers between 40000 and 50000.

References

References

1. "Sloane's A014080 : Factorions". OEIS Foundation.
2. "A046180 - OEIS".
3. {{cite OEIS. A000217. Triangular numbers
4. {{cite OEIS. A000326. Pentagonal numbers
5. {{cite OEIS. A000384. Hexagonal numbers
6. {{cite OEIS. A000014. Number of series-reduced trees with n nodes
7. "Sloane's A001110 : Square triangular numbers". OEIS Foundation.
8. "Sloane's A001006 : Motzkin numbers". OEIS Foundation.
9. "Sloane's A005900 : Octahedral numbers". OEIS Foundation.
10. "Sloane's A002559 : Markoff (or Markov) numbers". OEIS Foundation.
11. {{cite OEIS. A007053
12. {{Cite OEIS. A000979. Wagstaff primes
13. "Reversal-Addition Palindrome Test on 79".
14. {{cite OEIS. A000041. a(n) is the number of partitions of n (the partition numbers)
15. (22 September 2016). "The Promise of Immortality". Varegus Publishing.
16. {{Cite OEIS. A002182. Highly composite numbers
17. {{cite OEIS. A359013. Numbers k that can be written as the sum of a perfect square and a factorial in exactly 3 distinct ways
18. {{Cite OEIS. A000045. Fibonacci numbers
19. {{Cite OEIS. A054377. Primary pseudoperfect numbers
20. {{cite OEIS. A005727
21. {{cite OEIS. A000055. Number of trees with n unlabeled nodes
22. {{cite OEIS. A000011. Number of n-bead necklaces (turning over is allowed) where complements are equivalent
23. {{Cite OEIS. A003261. Woodall numbers
24. {{cite OEIS. A000013. Definition (1): Number of n-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed