21640955 has 16 divisors (see below), whose sum is σ = 29804544. Its totient is φ = 14776800.

The previous prime is 21640939. The next prime is 21640963. The reversal of 21640955 is 55904612.

It is a happy number.

It is not a de Polignac number, because 21640955 - 2⁴ = 21640939 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8030 + ... + 10380.

It is an arithmetic number, because the mean of its divisors is an integer number (1862784).

Almost surely, 2^21640955 is an apocalyptic number.

21640955 is a deficient number, since it is larger than the sum of its proper divisors (8163589).

21640955 is a wasteful number, since it uses less digits than its factorization.

21640955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2626.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 21640955 is about 4651.9839853551. The cubic root of 21640955 is about 278.6712339539.

The spelling of 21640955 in words is "twenty-one million, six hundred forty thousand, nine hundred fifty-five".