21331905 has 24 divisors (see below), whose sum is σ = 39704832. Its totient is φ = 9751392.

The previous prime is 21331903. The next prime is 21331963. The reversal of 21331905 is 50913312.

It is a happy number.

It is not a de Polignac number, because 21331905 - 2¹ = 21331903 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21331901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13777 + ... + 15246.

It is an arithmetic number, because the mean of its divisors is an integer number (1654368).

Almost surely, 2^21331905 is an apocalyptic number.

It is an amenable number.

21331905 is a deficient number, since it is larger than the sum of its proper divisors (18372927).

21331905 is a wasteful number, since it uses less digits than its factorization.

21331905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29045 (or 29038 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21331905 is about 4618.6475293099. The cubic root of 21331905 is about 277.3383199082.

The spelling of 21331905 in words is "twenty-one million, three hundred thirty-one thousand, nine hundred five".