21654765 has 72 divisors (see below), whose sum is σ = 42699384. Its totient is φ = 10137600.

The previous prime is 21654761. The next prime is 21654781. The reversal of 21654765 is 56745612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4356 + 21650409 = 66^2 + 4653^2 .

It is not a de Polignac number, because 21654765 - 2² = 21654761 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 an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21654761) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 223197 + ... + 223293.

It is an arithmetic number, because the mean of its divisors is an integer number (593047).

Almost surely, 2^21654765 is an apocalyptic number.

It is an amenable number.

21654765 is a deficient number, since it is larger than the sum of its proper divisors (21044619).

21654765 is a wasteful number, since it uses less digits than its factorization.

21654765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171 (or 157 counting only the distinct ones).

The product of its digits is 50400, while the sum is 36.

The square root of 21654765 is about 4653.4680615644. The cubic root of 21654765 is about 278.7304986123.

It can be divided in two parts, 216547 and 65, that added together give a palindrome (216612).

The spelling of 21654765 in words is "twenty-one million, six hundred fifty-four thousand, seven hundred sixty-five".