21718508 has 12 divisors (see below), whose sum is σ = 43437072. Its totient is φ = 9307920.

The previous prime is 21718457. The next prime is 21718513. The reversal of 21718508 is 80581712.

It is a happy number.

21718508 is an admirable 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, 387803 + ... + 387858.

It is an arithmetic number, because the mean of its divisors is an integer number (3619756).

Almost surely, 2^21718508 is an apocalyptic number.

21718508 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21718508 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21718508 is a wasteful number, since it uses less digits than its factorization.

21718508 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 775672 (or 775670 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21718508 is about 4660.3120067223. The cubic root of 21718508 is about 279.0037212112.

The spelling of 21718508 in words is "twenty-one million, seven hundred eighteen thousand, five hundred eight".