21908139 has 12 divisors (see below), whose sum is σ = 32108328. Its totient is φ = 13277440.

The previous prime is 21908119. The next prime is 21908141. The reversal of 21908139 is 93180912.

It is not a de Polignac number, because 21908139 - 2¹¹ = 21906091 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21908119) 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 11 ways as a sum of consecutive naturals, for example, 29814 + ... + 30539.

It is an arithmetic number, because the mean of its divisors is an integer number (2675694).

Almost surely, 2^21908139 is an apocalyptic number.

21908139 is a deficient number, since it is larger than the sum of its proper divisors (10200189).

21908139 is a wasteful number, since it uses less digits than its factorization.

21908139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60378 (or 60367 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 21908139 is about 4680.6131008662. The cubic root of 21908139 is about 279.8133918176.

The spelling of 21908139 in words is "twenty-one million, nine hundred eight thousand, one hundred thirty-nine".