21631365 has 48 divisors (see below), whose sum is σ = 43874688. Its totient is φ = 9652608.

The previous prime is 21631349. The next prime is 21631387. The reversal of 21631365 is 56313612.

21631365 is a `hidden beast` number, since 21 + 631 + 3 + 6 + 5 = 666.

It is not a de Polignac number, because 21631365 - 2⁴ = 21631349 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12747 + ... + 14343.

It is an arithmetic number, because the mean of its divisors is an integer number (914056).

Almost surely, 2^21631365 is an apocalyptic number.

It is an amenable number.

21631365 is an abundant number, since it is smaller than the sum of its proper divisors (22243323).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21631365 is a wasteful number, since it uses less digits than its factorization.

21631365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1658 (or 1655 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 21631365 is about 4650.9531281233. The cubic root of 21631365 is about 278.6300642984.

Adding to 21631365 its reverse (56313612), we get a palindrome (77944977).

The spelling of 21631365 in words is "twenty-one million, six hundred thirty-one thousand, three hundred sixty-five".