21908705 has 32 divisors (see below), whose sum is σ = 32659200. Its totient is φ = 13738752.

The previous prime is 21908701. The next prime is 21908713. The reversal of 21908705 is 50780912.

It is a cyclic number.

It is not a de Polignac number, because 21908705 - 2² = 21908701 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21908701) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 81311 + ... + 81579.

It is an arithmetic number, because the mean of its divisors is an integer number (1020600).

Almost surely, 2^21908705 is an apocalyptic number.

It is an amenable number.

21908705 is a deficient number, since it is larger than the sum of its proper divisors (10750495).

21908705 is a wasteful number, since it uses less digits than its factorization.

21908705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473.

The product of its (nonzero) digits is 5040, while the sum is 32.

The square root of 21908705 is about 4680.6735626403. The cubic root of 21908705 is about 279.8158014703.

The spelling of 21908705 in words is "twenty-one million, nine hundred eight thousand, seven hundred five".