21908691 has 32 divisors (see below), whose sum is σ = 39052800. Its totient is φ = 11858400.

The previous prime is 21908681. The next prime is 21908701. The reversal of 21908691 is 19680912.

It is an interprime number because it is at equal distance from previous prime (21908681) and next prime (21908701).

It is not a de Polignac number, because 21908691 - 2⁹ = 21908179 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21908611) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 541 + ... + 6641.

It is an arithmetic number, because the mean of its divisors is an integer number (1220400).

Almost surely, 2^21908691 is an apocalyptic number.

21908691 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21908691 is a deficient number, since it is larger than the sum of its proper divisors (17144109).

21908691 is a wasteful number, since it uses less digits than its factorization.

21908691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6136 (or 6130 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21908691 is about 4680.6720671288. The cubic root of 21908691 is about 279.8157418681.

The spelling of 21908691 in words is "twenty-one million, nine hundred eight thousand, six hundred ninety-one".