21908313 has 20 divisors (see below), whose sum is σ = 37403520. Its totient is φ = 12518712.

The previous prime is 21908303. The next prime is 21908317. The reversal of 21908313 is 31380912.

It is not a de Polignac number, because 21908313 - 2⁴ = 21908297 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21908317) 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 19 ways as a sum of consecutive naturals, for example, 18753 + ... + 19886.

It is an arithmetic number, because the mean of its divisors is an integer number (1870176).

Almost surely, 2^21908313 is an apocalyptic number.

It is an amenable number.

21908313 is a deficient number, since it is larger than the sum of its proper divisors (15495207).

21908313 is an equidigital number, since it uses as much as digits as its factorization.

21908313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38658 (or 38649 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21908313 is about 4680.6316881378. The cubic root of 21908313 is about 279.8141325986.

The spelling of 21908313 in words is "twenty-one million, nine hundred eight thousand, three hundred thirteen".