21690765 has 12 divisors (see below), whose sum is σ = 37597404. Its totient is φ = 11568384.

The previous prime is 21690743. The next prime is 21690787. The reversal of 21690765 is 56709612.

It is an interprime number because it is at equal distance from previous prime (21690743) and next prime (21690787).

It can be written as a sum of positive squares in 2 ways, for example, as 14040009 + 7650756 = 3747^2 + 2766^2 .

It is not a de Polignac number, because 21690765 - 2⁵ = 21690733 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240964 + ... + 241053.

It is an arithmetic number, because the mean of its divisors is an integer number (3133117).

Almost surely, 2^21690765 is an apocalyptic number.

It is an amenable number.

21690765 is a deficient number, since it is larger than the sum of its proper divisors (15906639).

21690765 is a wasteful number, since it uses less digits than its factorization.

21690765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 482028 (or 482025 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 21690765 is about 4657.3345381237. The cubic root of 21690765 is about 278.8848717578.

The spelling of 21690765 in words is "twenty-one million, six hundred ninety thousand, seven hundred sixty-five".