21310513 has 4 divisors (see below), whose sum is σ = 24354880. Its totient is φ = 18266148.

The previous prime is 21310493. The next prime is 21310517. The reversal of 21310513 is 31501312.

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.

It is a cyclic number.

It is not a de Polignac number, because 21310513 - 2¹³ = 21302321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21310517) 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, 1522173 + ... + 1522186.

It is an arithmetic number, because the mean of its divisors is an integer number (6088720).

Almost surely, 2^21310513 is an apocalyptic number.

It is an amenable number.

21310513 is a deficient number, since it is larger than the sum of its proper divisors (3044367).

21310513 is an equidigital number, since it uses as much as digits as its factorization.

21310513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3044366.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21310513 is about 4616.3311189732. The cubic root of 21310513 is about 277.2455823613.

Adding to 21310513 its reverse (31501312), we get a palindrome (52811825).

The spelling of 21310513 in words is "twenty-one million, three hundred ten thousand, five hundred thirteen".