21684928 has 56 divisors (see below), whose sum is σ = 48006000. Its totient is φ = 9658368.

The previous prime is 21684917. The next prime is 21684931. The reversal of 21684928 is 82948612.

It is a super-2 number, since 2×21684928² = 940472204730368, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20148 + ... + 21196.

It is an arithmetic number, because the mean of its divisors is an integer number (857250).

Almost surely, 2^21684928 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21684928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24003000).

21684928 is an abundant number, since it is smaller than the sum of its proper divisors (26321072).

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

21684928 is a wasteful number, since it uses less digits than its factorization.

21684928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1097 (or 1087 counting only the distinct ones).

The product of its digits is 55296, while the sum is 40.

The square root of 21684928 is about 4656.7078499730. The cubic root of 21684928 is about 278.8598534757.

The spelling of 21684928 in words is "twenty-one million, six hundred eighty-four thousand, nine hundred twenty-eight".