21208613 has 2 divisors, whose sum is σ = 21208614. Its totient is φ = 21208612.

The previous prime is 21208601. The next prime is 21208633. The reversal of 21208613 is 31680212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16337764 + 4870849 = 4042^2 + 2207^2 .

It is a cyclic number.

It is not a de Polignac number, because 21208613 - 2⁶ = 21208549 is a prime.

It is a Chen prime.

It is equal to p_1342292 and since 21208613 and 1342292 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21208633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604306 + 10604307.

It is an arithmetic number, because the mean of its divisors is an integer number (10604307).

Almost surely, 2^21208613 is an apocalyptic number.

It is an amenable number.

21208613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21208613 is an equidigital number, since it uses as much as digits as its factorization.

21208613 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21208613 is about 4605.2809903414. The cubic root of 21208613 is about 276.8029764916.

Adding to 21208613 its reverse (31680212), we get a palindrome (52888825).

The spelling of 21208613 in words is "twenty-one million, two hundred eight thousand, six hundred thirteen".