21713728 has 28 divisors (see below), whose sum is σ = 43382692. Its totient is φ = 10782720.

The previous prime is 21713707. The next prime is 21713737. The reversal of 21713728 is 82731712.

It can be written as a sum of positive squares in 2 ways, for example, as 9935104 + 11778624 = 3152^2 + 3432^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21713728.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8968 + ... + 11128.

Almost surely, 2^21713728 is an apocalyptic number.

It is an amenable number.

21713728 is a deficient number, since it is larger than the sum of its proper divisors (21668964).

21713728 is a wasteful number, since it uses less digits than its factorization.

21713728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2330 (or 2320 counting only the distinct ones).

The product of its digits is 4704, while the sum is 31.

The square root of 21713728 is about 4659.7991373020. The cubic root of 21713728 is about 278.9832511796.

The spelling of 21713728 in words is "twenty-one million, seven hundred thirteen thousand, seven hundred twenty-eight".