21493613 has 2 divisors, whose sum is σ = 21493614. Its totient is φ = 21493612.

The previous prime is 21493603. The next prime is 21493621. The reversal of 21493613 is 31639412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14455204 + 7038409 = 3802^2 + 2653^2 .

It is a cyclic number.

It is not a de Polignac number, because 21493613 - 2¹⁰ = 21492589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21493603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746806 + 10746807.

It is an arithmetic number, because the mean of its divisors is an integer number (10746807).

Almost surely, 2^21493613 is an apocalyptic number.

It is an amenable number.

21493613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493613 is an equidigital number, since it uses as much as digits as its factorization.

21493613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 29.

The square root of 21493613 is about 4636.1204686677. The cubic root of 21493613 is about 278.0373507084.

The spelling of 21493613 in words is "twenty-one million, four hundred ninety-three thousand, six hundred thirteen".