21308579 has 2 divisors, whose sum is σ = 21308580. Its totient is φ = 21308578.

The previous prime is 21308543. The next prime is 21308611. The reversal of 21308579 is 97580312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21308579 - 2²⁰ = 20260003 is a prime.

It is not a weakly prime, because it can be changed into another prime (21308509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10654289 + 10654290.

It is an arithmetic number, because the mean of its divisors is an integer number (10654290).

Almost surely, 2^21308579 is an apocalyptic number.

21308579 is a deficient number, since it is larger than the sum of its proper divisors (1).

21308579 is an equidigital number, since it uses as much as digits as its factorization.

21308579 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21308579 is about 4616.1216405117. The cubic root of 21308579 is about 277.2371951210.

The spelling of 21308579 in words is "twenty-one million, three hundred eight thousand, five hundred seventy-nine".