21604157765672 has 16 divisors (see below), whose sum is σ = 40514881395060. Its totient is φ = 10800189393664.

The previous prime is 21604157765653. The next prime is 21604157765677. The reversal of 21604157765672 is 27656775140612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21587230194436 + 16927571236 = 4646206^2 + 130106^2 .

It is a super-3 number, since 3×21604157765672³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21604157765677) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 236137553 + ... + 236229024.

Almost surely, 2^{21604157765672} is an apocalyptic number.

It is an amenable number.

21604157765672 is a deficient number, since it is larger than the sum of its proper divisors (18910723629388).

21604157765672 is a wasteful number, since it uses less digits than its factorization.

21604157765672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 472372300 (or 472372296 counting only the distinct ones).

The product of its (nonzero) digits is 29635200, while the sum is 59.

The spelling of 21604157765672 in words is "twenty-one trillion, six hundred four billion, one hundred fifty-seven million, seven hundred sixty-five thousand, six hundred seventy-two".