21917008 has 10 divisors (see below), whose sum is σ = 42464234. Its totient is φ = 10958496.

The previous prime is 21917003. The next prime is 21917023. The reversal of 21917008 is 80071912.

It can be written as a sum of positive squares in only one way, i.e., 19820304 + 2096704 = 4452^2 + 1448^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 684891 + ... + 684922.

Almost surely, 2^21917008 is an apocalyptic number.

It is an amenable number.

21917008 is a deficient number, since it is larger than the sum of its proper divisors (20547226).

21917008 is a wasteful number, since it uses less digits than its factorization.

21917008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1369821 (or 1369815 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21917008 is about 4681.5604236195. The cubic root of 21917008 is about 279.8511453692.

The spelling of 21917008 in words is "twenty-one million, nine hundred seventeen thousand, eight".