21721157604 has 36 divisors (see below), whose sum is σ = 55235054784. Its totient is φ = 7197028272.

The previous prime is 21721157597. The next prime is 21721157609. The reversal of 21721157604 is 40675112712.

21721157604 is a `hidden beast` number, since 2 + 1 + 72 + 11 + 576 + 0 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is not an unprimeable number, because it can be changed into a prime (21721157609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1800472 + ... + 1812495.

Almost surely, 2^21721157604 is an apocalyptic number.

It is an amenable number.

21721157604 is an abundant number, since it is smaller than the sum of its proper divisors (33513897180).

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

21721157604 is a wasteful number, since it uses less digits than its factorization.

21721157604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3613144 (or 3613139 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The spelling of 21721157604 in words is "twenty-one billion, seven hundred twenty-one million, one hundred fifty-seven thousand, six hundred four".