21513928 has 16 divisors (see below), whose sum is σ = 42462000. Its totient is φ = 10190736.

The previous prime is 21513893. The next prime is 21513929. The reversal of 21513928 is 82931512.

It is a self number, because there is not a number n which added to its sum of digits gives 21513928.

It is not an unprimeable number, because it can be changed into a prime (21513929) 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, 70618 + ... + 70921.

It is an arithmetic number, because the mean of its divisors is an integer number (2653875).

Almost surely, 2^21513928 is an apocalyptic number.

It is an amenable number.

21513928 is a deficient number, since it is larger than the sum of its proper divisors (20948072).

21513928 is a wasteful number, since it uses less digits than its factorization.

21513928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141564 (or 141560 counting only the distinct ones).

The product of its digits is 4320, while the sum is 31.

The square root of 21513928 is about 4638.3108994547. The cubic root of 21513928 is about 278.1249201363.

The spelling of 21513928 in words is "twenty-one million, five hundred thirteen thousand, nine hundred twenty-eight".