21909965 has 16 divisors (see below), whose sum is σ = 32780160. Its totient is φ = 13657920.

The previous prime is 21909941. The next prime is 21909977. The reversal of 21909965 is 56990912.

It is not a de Polignac number, because 21909965 - 2²⁰ = 20861389 is a prime.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 28070 + ... + 28839.

It is an arithmetic number, because the mean of its divisors is an integer number (2048760).

Almost surely, 2^21909965 is an apocalyptic number.

It is an amenable number.

21909965 is a deficient number, since it is larger than the sum of its proper divisors (10870195).

21909965 is a wasteful number, since it uses less digits than its factorization.

21909965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56932.

The product of its (nonzero) digits is 43740, while the sum is 41.

The square root of 21909965 is about 4680.8081567182. The cubic root of 21909965 is about 279.8211655657.

The spelling of 21909965 in words is "twenty-one million, nine hundred nine thousand, nine hundred sixty-five".