21312525 has 24 divisors (see below), whose sum is σ = 37948960. Its totient is φ = 10491840.

The previous prime is 21312523. The next prime is 21312539. The reversal of 21312525 is 52521312.

It is not a de Polignac number, because 21312525 - 2¹ = 21312523 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312523) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9955 + ... + 11904.

Almost surely, 2^21312525 is an apocalyptic number.

21312525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21312525 is a deficient number, since it is larger than the sum of its proper divisors (16636435).

21312525 is a wasteful number, since it uses less digits than its factorization.

21312525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21885 (or 21880 counting only the distinct ones).

The product of its digits is 600, while the sum is 21.

The square root of 21312525 is about 4616.5490358059. The cubic root of 21312525 is about 277.2543073281.

Adding to 21312525 its reverse (52521312), we get a palindrome (73833837).

It can be divided in two parts, 2131 and 2525, that added together give a triangular number (4656 = T₉₆).

The spelling of 21312525 in words is "twenty-one million, three hundred twelve thousand, five hundred twenty-five".