40,000 (forty thousand) is the natural number that comes after 39,999 and before 40,001. It is the square of 200.
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
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
43390 = number of primes . 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 44721 = smallest positive integer such that the expression − ≤ 10−9 44944 = palindromic square
45000 to 45999
45360 = highly composite number; first number to have 100 factors (including one and itself)
46000 to 46999
46233 = sum of the first eight factorials
46368 = Fibonacci number
46656 = 36, 66, 3-smooth number
46657 = Carmichael number
47000 to 47999
47058 = primary pseudoperfect number
47160 = 10-th derivative of xx at x=1
47321/33461 ≈ √2
48000 to 48999
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.