21997508 has 24 divisors (see below), whose sum is σ = 41847960. Its totient is φ = 10056960.

The previous prime is 21997487. The next prime is 21997513. The reversal of 21997508 is 80579912.

It can be written as a sum of positive squares in 4 ways, for example, as 2795584 + 19201924 = 1672^2 + 4382^2 .

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, 3728 + ... + 7608.

It is an arithmetic number, because the mean of its divisors is an integer number (1743665).

Almost surely, 2^21997508 is an apocalyptic number.

It is an amenable number.

21997508 is a deficient number, since it is larger than the sum of its proper divisors (19850452).

21997508 is a wasteful number, since it uses less digits than its factorization.

21997508 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4007 (or 4005 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 21997508 is about 4690.1501042078. The cubic root of 21997508 is about 280.1933528448.

The spelling of 21997508 in words is "twenty-one million, nine hundred ninety-seven thousand, five hundred eight".