21377564 has 48 divisors (see below), whose sum is σ = 42542976. Its totient is φ = 9331200.

The previous prime is 21377561. The next prime is 21377567. The reversal of 21377564 is 46577312.

It is an interprime number because it is at equal distance from previous prime (21377561) and next prime (21377567).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21377561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78749 + ... + 79019.

It is an arithmetic number, because the mean of its divisors is an integer number (886312).

Almost surely, 2^21377564 is an apocalyptic number.

It is an amenable number.

21377564 is a deficient number, since it is larger than the sum of its proper divisors (21165412).

21377564 is a wasteful number, since it uses less digits than its factorization.

21377564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 366 (or 364 counting only the distinct ones).

The product of its digits is 35280, while the sum is 35.

The square root of 21377564 is about 4623.5877843943. The cubic root of 21377564 is about 277.5360513722.

It can be divided in two parts, 213 and 77564, that added together give a palindrome (77777).

The spelling of 21377564 in words is "twenty-one million, three hundred seventy-seven thousand, five hundred sixty-four".