21642013 has 2 divisors, whose sum is σ = 21642014. Its totient is φ = 21642012.

The previous prime is 21641993. The next prime is 21642017. The reversal of 21642013 is 31024612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20958084 + 683929 = 4578^2 + 827^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642013 - 2⁵ = 21641981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21642017) 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, 10821006 + 10821007.

It is an arithmetic number, because the mean of its divisors is an integer number (10821007).

Almost surely, 2^21642013 is an apocalyptic number.

It is an amenable number.

21642013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642013 is an equidigital number, since it uses as much as digits as its factorization.

21642013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21642013 is about 4652.0976988881. The cubic root of 21642013 is about 278.6757751793.

Adding to 21642013 its reverse (31024612), we get a palindrome (52666625).

The spelling of 21642013 in words is "twenty-one million, six hundred forty-two thousand, thirteen".