21287108 has 12 divisors (see below), whose sum is σ = 37302720. Its totient is φ = 10629192.

The previous prime is 21287089. The next prime is 21287129. The reversal of 21287108 is 80178212.

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, 185 + ... + 6527.

It is an arithmetic number, because the mean of its divisors is an integer number (3108560).

Almost surely, 2^21287108 is an apocalyptic number.

It is an amenable number.

21287108 is a deficient number, since it is larger than the sum of its proper divisors (16015612).

21287108 is a wasteful number, since it uses less digits than its factorization.

21287108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7186 (or 7184 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21287108 is about 4613.7954007520. The cubic root of 21287108 is about 277.1440470319.

The spelling of 21287108 in words is "twenty-one million, two hundred eighty-seven thousand, one hundred eight".