21664307520 has 224 divisors, whose sum is σ = 76680608640. Its totient is φ = 5757972480.

The previous prime is 21664307501. The next prime is 21664307521. The reversal of 21664307520 is 2570346612.

21664307520 is a `hidden beast` number, since 2 + 1 + 6 + 643 + 0 + 7 + 5 + 2 + 0 = 666.

It is a super-2 number, since 2×21664307520² (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 a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664307521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2700315 + ... + 2708325.

Almost surely, 2^21664307520 is an apocalyptic number.

21664307520 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 21664307520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38340304320).

21664307520 is an abundant number, since it is smaller than the sum of its proper divisors (55016301120).

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

21664307520 is a wasteful number, since it uses less digits than its factorization.

21664307520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8350 (or 8334 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

The spelling of 21664307520 in words is "twenty-one billion, six hundred sixty-four million, three hundred seven thousand, five hundred twenty".