21621916800 has 576 divisors, whose sum is σ = 84971034720. Its totient is φ = 5191680000.

The previous prime is 21621916787. The next prime is 21621916829. The reversal of 21621916800 is 861912612.

21621916800 is a `hidden beast` number, since 21 + 621 + 9 + 1 + 6 + 8 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

It is a super-2 number, since 2×21621916800² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 41500540 + ... + 41501060.

Almost surely, 2^21621916800 is an apocalyptic number.

21621916800 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21621916800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42485517360).

21621916800 is an abundant number, since it is smaller than the sum of its proper divisors (63349117920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21621916800 is a wasteful number, since it uses less digits than its factorization.

21621916800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 693 (or 673 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The spelling of 21621916800 in words is "twenty-one billion, six hundred twenty-one million, nine hundred sixteen thousand, eight hundred".