21072513 has 24 divisors (see below), whose sum is σ = 35299264. Its totient is φ = 10945440.

The previous prime is 21072487. The next prime is 21072517. The reversal of 21072513 is 31527012.

It is not a de Polignac number, because 21072513 - 2⁵ = 21072481 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21072513.

It is not an unprimeable number, because it can be changed into a prime (21072517) 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, 1606 + ... + 6687.

Almost surely, 2^21072513 is an apocalyptic number.

It is an amenable number.

21072513 is a deficient number, since it is larger than the sum of its proper divisors (14226751).

21072513 is a wasteful number, since it uses less digits than its factorization.

21072513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8325 (or 8314 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21072513 is about 4590.4806937836. The cubic root of 21072513 is about 276.2096050078.

Adding to 21072513 its reverse (31527012), we get a palindrome (52599525).

The spelling of 21072513 in words is "twenty-one million, seventy-two thousand, five hundred thirteen".