21251545636 has 6 divisors (see below), whose sum is σ = 37190204870. Its totient is φ = 10625772816.

The previous prime is 21251545597. The next prime is 21251545697. The reversal of 21251545636 is 63654515212.

It can be written as a sum of positive squares in only one way, i.e., 11205492736 + 10046052900 = 105856^2 + 100230^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2656443201 + ... + 2656443208.

Almost surely, 2^21251545636 is an apocalyptic number.

It is an amenable number.

21251545636 is a deficient number, since it is larger than the sum of its proper divisors (15938659234).

21251545636 is a wasteful number, since it uses less digits than its factorization.

21251545636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5312886413 (or 5312886411 counting only the distinct ones).

The product of its digits is 216000, while the sum is 40.

The spelling of 21251545636 in words is "twenty-one billion, two hundred fifty-one million, five hundred forty-five thousand, six hundred thirty-six".