21915923 has 2 divisors, whose sum is σ = 21915924. Its totient is φ = 21915922.

The previous prime is 21915917. The next prime is 21915931. The reversal of 21915923 is 32951912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21915923 - 2²² = 17721619 is a prime.

It is equal to p_1384259 and since 21915923 and 1384259 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21915923.

It is not a weakly prime, because it can be changed into another prime (21915953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10957961 + 10957962.

It is an arithmetic number, because the mean of its divisors is an integer number (10957962).

Almost surely, 2^21915923 is an apocalyptic number.

21915923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21915923 is an equidigital number, since it uses as much as digits as its factorization.

21915923 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4860, while the sum is 32.

The square root of 21915923 is about 4681.4445420191. Note that the first 3 decimals coincide. The cubic root of 21915923 is about 279.8465272890.

The spelling of 21915923 in words is "twenty-one million, nine hundred fifteen thousand, nine hundred twenty-three".