21908390 has 24 divisors (see below), whose sum is σ = 45874512. Its totient is φ = 7511280.

The previous prime is 21908377. The next prime is 21908401. The reversal of 21908390 is 9380912.

It is a congruent number.

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 11 ways as a sum of consecutive naturals, for example, 21866 + ... + 22845.

It is an arithmetic number, because the mean of its divisors is an integer number (1911438).

Almost surely, 2^21908390 is an apocalyptic number.

21908390 is an abundant number, since it is smaller than the sum of its proper divisors (23966122).

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

21908390 is a wasteful number, since it uses less digits than its factorization.

21908390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44732 (or 44725 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 21908390 is about 4680.6399135161. The cubic root of 21908390 is about 279.8144604143.

The spelling of 21908390 in words is "twenty-one million, nine hundred eight thousand, three hundred ninety".