21072013 has 4 divisors (see below), whose sum is σ = 21083328. Its totient is φ = 21060700.

The previous prime is 21072011. The next prime is 21072017. The reversal of 21072013 is 31027012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21072013 - 2¹ = 21072011 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2131 + ... + 6832.

It is an arithmetic number, because the mean of its divisors is an integer number (5270832).

Almost surely, 2^21072013 is an apocalyptic number.

It is an amenable number.

21072013 is a deficient number, since it is larger than the sum of its proper divisors (11315).

21072013 is an equidigital number, since it uses as much as digits as its factorization.

21072013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11314.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21072013 is about 4590.4262329331. The cubic root of 21072013 is about 276.2074203942.

Adding to 21072013 its reverse (31027012), we get a palindrome (52099025).

The spelling of 21072013 in words is "twenty-one million, seventy-two thousand, thirteen".