21257708 has 12 divisors (see below), whose sum is σ = 37322040. Its totient is φ = 10594272.

The previous prime is 21257699. The next prime is 21257729. The reversal of 21257708 is 80775212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7238 + ... + 9741.

It is an arithmetic number, because the mean of its divisors is an integer number (3110170).

Almost surely, 2^21257708 is an apocalyptic number.

It is an amenable number.

21257708 is a deficient number, since it is larger than the sum of its proper divisors (16064332).

21257708 is a wasteful number, since it uses less digits than its factorization.

21257708 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17296 (or 17294 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21257708 is about 4610.6082028296. The cubic root of 21257708 is about 277.0163987390.

The spelling of 21257708 in words is "twenty-one million, two hundred fifty-seven thousand, seven hundred eight".