21313913 has 2 divisors, whose sum is σ = 21313914. Its totient is φ = 21313912.

The previous prime is 21313909. The next prime is 21313931. The reversal of 21313913 is 31931312.

Together with next prime (21313931) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17749369 + 3564544 = 4213^2 + 1888^2 .

It is a cyclic number.

It is not a de Polignac number, because 21313913 - 2² = 21313909 is a prime.

It is not a weakly prime, because it can be changed into another prime (21313933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656956 + 10656957.

It is an arithmetic number, because the mean of its divisors is an integer number (10656957).

Almost surely, 2^21313913 is an apocalyptic number.

It is an amenable number.

21313913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21313913 is an equidigital number, since it uses as much as digits as its factorization.

21313913 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 486, while the sum is 23.

The square root of 21313913 is about 4616.6993620984. The cubic root of 21313913 is about 277.2603260210.

The spelling of 21313913 in words is "twenty-one million, three hundred thirteen thousand, nine hundred thirteen".