21915765 has 40 divisors (see below), whose sum is σ = 40066488. Its totient is φ = 11456640.

The previous prime is 21915763. The next prime is 21915769. The reversal of 21915765 is 56751912.

It can be written as a sum of positive squares in 4 ways, for example, as 4626801 + 17288964 = 2151^2 + 4158^2 .

It is not a de Polignac number, because 21915765 - 2¹ = 21915763 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21915763) by changing a digit.

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 39 ways as a sum of consecutive naturals, for example, 20955 + ... + 21975.

Almost surely, 2^21915765 is an apocalyptic number.

It is an amenable number.

21915765 is a deficient number, since it is larger than the sum of its proper divisors (18150723).

21915765 is a wasteful number, since it uses less digits than its factorization.

21915765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1091 (or 1082 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 21915765 is about 4681.4276668555. The cubic root of 21915765 is about 279.8458547816.

The spelling of 21915765 in words is "twenty-one million, nine hundred fifteen thousand, seven hundred sixty-five".