21864613 has 2 divisors, whose sum is σ = 21864614. Its totient is φ = 21864612.

The previous prime is 21864587. The next prime is 21864617. The reversal of 21864613 is 31646812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12236004 + 9628609 = 3498^2 + 3103^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21864613 is a prime.

It is a super-2 number, since 2×21864613² = 956122603279538, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21864617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932306 + 10932307.

It is an arithmetic number, because the mean of its divisors is an integer number (10932307).

Almost surely, 2^21864613 is an apocalyptic number.

It is an amenable number.

21864613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21864613 is an equidigital number, since it uses as much as digits as its factorization.

21864613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 31.

The square root of 21864613 is about 4675.9611846122. The cubic root of 21864613 is about 279.6279625234.

The spelling of 21864613 in words is "twenty-one million, eight hundred sixty-four thousand, six hundred thirteen".