21820959 has 12 divisors (see below), whose sum is σ = 31721976. Its totient is φ = 14453712.

The previous prime is 21820957. The next prime is 21820991. The reversal of 21820959 is 95902812.

It is not a de Polignac number, because 21820959 - 2¹ = 21820957 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820957) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6309 + ... + 9134.

It is an arithmetic number, because the mean of its divisors is an integer number (2643498).

Almost surely, 2^21820959 is an apocalyptic number.

21820959 is a deficient number, since it is larger than the sum of its proper divisors (9901017).

21820959 is a wasteful number, since it uses less digits than its factorization.

21820959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15606 (or 15603 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 21820959 is about 4671.2909350628. The cubic root of 21820959 is about 279.4417405824.

The spelling of 21820959 in words is "twenty-one million, eight hundred twenty thousand, nine hundred fifty-nine".