21312013 has 4 divisors (see below), whose sum is σ = 22046940. Its totient is φ = 20577088.

The previous prime is 21312001. The next prime is 21312017. The reversal of 21312013 is 31021312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14768649 + 6543364 = 3843^2 + 2558^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312013 - 2⁵ = 21311981 is a prime.

It is a super-2 number, since 2×21312013² = 908403796224338, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311984 and 21312002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312017) 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, 367420 + ... + 367477.

It is an arithmetic number, because the mean of its divisors is an integer number (5511735).

Almost surely, 2^21312013 is an apocalyptic number.

It is an amenable number.

21312013 is a deficient number, since it is larger than the sum of its proper divisors (734927).

21312013 is an equidigital number, since it uses as much as digits as its factorization.

21312013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 734926.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21312013 is about 4616.4935827964. The cubic root of 21312013 is about 277.2520871103.

Adding to 21312013 its reverse (31021312), we get a palindrome (52333325).

The spelling of 21312013 in words is "twenty-one million, three hundred twelve thousand, thirteen".