21292728 has 32 divisors (see below), whose sum is σ = 55069200. Its totient is φ = 6852608.

The previous prime is 21292717. The next prime is 21292729. The reversal of 21292728 is 82729212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21292729) 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, 14601 + ... + 15992.

Almost surely, 2^21292728 is an apocalyptic number.

It is an amenable number.

21292728 is an abundant number, since it is smaller than the sum of its proper divisors (33776472).

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

21292728 is a wasteful number, since it uses less digits than its factorization.

21292728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30631 (or 30627 counting only the distinct ones).

The product of its digits is 8064, while the sum is 33.

The square root of 21292728 is about 4614.4044036040. The cubic root of 21292728 is about 277.1684344451.

The spelling of 21292728 in words is "twenty-one million, two hundred ninety-two thousand, seven hundred twenty-eight".