21557396 has 24 divisors (see below), whose sum is σ = 44034816. Its totient is φ = 9041760.

The previous prime is 21557387. The next prime is 21557401. The reversal of 21557396 is 69375512.

It is a happy number.

It is a congruent number.

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, 6875 + ... + 9506.

It is an arithmetic number, because the mean of its divisors is an integer number (1834784).

Almost surely, 2^21557396 is an apocalyptic number.

It is an amenable number.

21557396 is an abundant number, since it is smaller than the sum of its proper divisors (22477420).

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

21557396 is a wasteful number, since it uses less digits than its factorization.

21557396 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16439 (or 16437 counting only the distinct ones).

The product of its digits is 56700, while the sum is 38.

The square root of 21557396 is about 4642.9942924798. The cubic root of 21557396 is about 278.3121074168.

The spelling of 21557396 in words is "twenty-one million, five hundred fifty-seven thousand, three hundred ninety-six".