21579581 has 2 divisors, whose sum is σ = 21579582. Its totient is φ = 21579580.

The previous prime is 21579557. The next prime is 21579587. The reversal of 21579581 is 18597512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21473956 + 105625 = 4634^2 + 325^2 .

It is a cyclic number.

It is not a de Polignac number, because 21579581 - 2⁶ = 21579517 is a prime.

It is a super-2 number, since 2×21579581² = 931356632271122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21579587) 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, 10789790 + 10789791.

It is an arithmetic number, because the mean of its divisors is an integer number (10789791).

Almost surely, 2^21579581 is an apocalyptic number.

It is an amenable number.

21579581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21579581 is an equidigital number, since it uses as much as digits as its factorization.

21579581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25200, while the sum is 38.

The square root of 21579581 is about 4645.3827614094. The cubic root of 21579581 is about 278.4075462363.

The spelling of 21579581 in words is "twenty-one million, five hundred seventy-nine thousand, five hundred eighty-one".