21391108 has 6 divisors (see below), whose sum is σ = 37434446. Its totient is φ = 10695552.

The previous prime is 21391091. The next prime is 21391129. The reversal of 21391108 is 80119312.

It can be written as a sum of positive squares in only one way, i.e., 21362884 + 28224 = 4622^2 + 168^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2673885 + ... + 2673892.

Almost surely, 2^21391108 is an apocalyptic number.

It is an amenable number.

21391108 is a deficient number, since it is larger than the sum of its proper divisors (16043338).

21391108 is a wasteful number, since it uses less digits than its factorization.

21391108 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5347781 (or 5347779 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 21391108 is about 4625.0522159215. The cubic root of 21391108 is about 277.5946510443.

The spelling of 21391108 in words is "twenty-one million, three hundred ninety-one thousand, one hundred eight".