21991634576 has 20 divisors (see below), whose sum is σ = 42651559932. Its totient is φ = 10984780416.

The previous prime is 21991634573. The next prime is 21991634627. The reversal of 21991634576 is 67543619912.

It can be written as a sum of positive squares in 2 ways, for example, as 9385734400 + 12605900176 = 96880^2 + 112276^2 .

It is not an unprimeable number, because it can be changed into a prime (21991634573) 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, 673355 + ... + 705258.

Almost surely, 2^21991634576 is an apocalyptic number.

It is an amenable number.

21991634576 is a deficient number, since it is larger than the sum of its proper divisors (20659925356).

21991634576 is a wasteful number, since it uses less digits than its factorization.

21991634576 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1379618 (or 1379612 counting only the distinct ones).

The product of its digits is 2449440, while the sum is 53.

The spelling of 21991634576 in words is "twenty-one billion, nine hundred ninety-one million, six hundred thirty-four thousand, five hundred seventy-six".