21028973556 has 24 divisors (see below), whose sum is σ = 49148458240. Its totient is φ = 6998107392.

The previous prime is 21028973533. The next prime is 21028973557. The reversal of 21028973556 is 65537982012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21028973557) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1436221 + ... + 1450788.

Almost surely, 2^21028973556 is an apocalyptic number.

It is an amenable number.

21028973556 is an abundant number, since it is smaller than the sum of its proper divisors (28119484684).

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

21028973556 is a wasteful number, since it uses less digits than its factorization.

21028973556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2887623 (or 2887621 counting only the distinct ones).

The product of its (nonzero) digits is 907200, while the sum is 48.

The spelling of 21028973556 in words is "twenty-one billion, twenty-eight million, nine hundred seventy-three thousand, five hundred fifty-six".