21613213 has 2 divisors, whose sum is σ = 21613214. Its totient is φ = 21613212.

The previous prime is 21613199. The next prime is 21613237. The reversal of 21613213 is 31231612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19123129 + 2490084 = 4373^2 + 1578^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21613213 is a prime.

It is a plaindrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21613243) 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, 10806606 + 10806607.

It is an arithmetic number, because the mean of its divisors is an integer number (10806607).

Almost surely, 2^21613213 is an apocalyptic number.

It is an amenable number.

21613213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21613213 is an equidigital number, since it uses as much as digits as its factorization.

21613213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 19.

The square root of 21613213 is about 4649.0012905999. The cubic root of 21613213 is about 278.5521048429.

Adding to 21613213 its reverse (31231612), we get a palindrome (52844825).

The spelling of 21613213 in words is "twenty-one million, six hundred thirteen thousand, two hundred thirteen".