21657424 has 20 divisors (see below), whose sum is σ = 42118336. Its totient is φ = 10788192.

The previous prime is 21657407. The next prime is 21657431. The reversal of 21657424 is 42475612.

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, 2137 + ... + 6919.

Almost surely, 2^21657424 is an apocalyptic number.

It is an amenable number.

21657424 is a deficient number, since it is larger than the sum of its proper divisors (20460912).

21657424 is a wasteful number, since it uses less digits than its factorization.

21657424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5074 (or 5068 counting only the distinct ones).

The product of its digits is 13440, while the sum is 31.

The square root of 21657424 is about 4653.7537536917. The cubic root of 21657424 is about 278.7419066336.

The spelling of 21657424 in words is "twenty-one million, six hundred fifty-seven thousand, four hundred twenty-four".