21664972800 has 450 divisors, whose sum is σ = 80382497118. Its totient is φ = 5768478720.

The previous prime is 21664972741. The next prime is 21664972817. The reversal of 21664972800 is 827946612.

It is a happy number.

21664972800 is a `hidden beast` number, since 21 + 66 + 497 + 2 + 80 + 0 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 260112384 + 21404860416 = 16128^2 + 146304^2 .

It is a tau number, because it is divible by the number of its divisors (450).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 33177274 + ... + 33177926.

Almost surely, 2^21664972800 is an apocalyptic number.

21664972800 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 21664972800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40191248559).

21664972800 is an abundant number, since it is smaller than the sum of its proper divisors (58717524318).

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

21664972800 is an frugal number, since it uses more digits than its factorization.

21664972800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 703 (or 663 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 21664972800 in words is "twenty-one billion, six hundred sixty-four million, nine hundred seventy-two thousand, eight hundred".