21513513 has 16 divisors (see below), whose sum is σ = 32848256. Its totient is φ = 12268800.

The previous prime is 21513511. The next prime is 21513523. The reversal of 21513513 is 31531512.

It is not a de Polignac number, because 21513513 - 2¹ = 21513511 is a prime.

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

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21513513.

It is not an unprimeable number, because it can be changed into a prime (21513511) 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, 17313 + ... + 18513.

It is an arithmetic number, because the mean of its divisors is an integer number (2053016).

Almost surely, 2^21513513 is an apocalyptic number.

It is an amenable number.

21513513 is a deficient number, since it is larger than the sum of its proper divisors (11334743).

21513513 is a wasteful number, since it uses less digits than its factorization.

21513513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2064.

The product of its digits is 450, while the sum is 21.

The square root of 21513513 is about 4638.2661631260. The cubic root of 21513513 is about 278.1231317974.

The spelling of 21513513 in words is "twenty-one million, five hundred thirteen thousand, five hundred thirteen".