21242564 has 24 divisors (see below), whose sum is σ = 43857408. Its totient is φ = 8809920.

The previous prime is 21242563. The next prime is 21242569. The reversal of 21242564 is 46524212.

It is not an unprimeable number, because it can be changed into a prime (21242563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11369 + ... + 13104.

It is an arithmetic number, because the mean of its divisors is an integer number (1827392).

Almost surely, 2^21242564 is an apocalyptic number.

It is an amenable number.

21242564 is an abundant number, since it is smaller than the sum of its proper divisors (22614844).

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

21242564 is a wasteful number, since it uses less digits than its factorization.

21242564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24515 (or 24513 counting only the distinct ones).

The product of its digits is 3840, while the sum is 26.

The square root of 21242564 is about 4608.9656106333. The cubic root of 21242564 is about 276.9506009125.

Adding to 21242564 its reverse (46524212), we get a palindrome (67766776).

The spelling of 21242564 in words is "twenty-one million, two hundred forty-two thousand, five hundred sixty-four".