21579493 has 16 divisors (see below), whose sum is σ = 23845360. Its totient is φ = 19408896.

The previous prime is 21579491. The next prime is 21579517. The reversal of 21579493 is 39497512.

It can be written as a sum of positive squares in 8 ways, for example, as 1085764 + 20493729 = 1042^2 + 4527^2 .

It is not a de Polignac number, because 21579493 - 2¹ = 21579491 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21579491) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 137371 + ... + 137527.

It is an arithmetic number, because the mean of its divisors is an integer number (1490335).

Almost surely, 2^21579493 is an apocalyptic number.

It is an amenable number.

21579493 is a deficient number, since it is larger than the sum of its proper divisors (2265867).

21579493 is a wasteful number, since it uses less digits than its factorization.

21579493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 376.

The product of its digits is 68040, while the sum is 40.

The square root of 21579493 is about 4645.3732896292. The cubic root of 21579493 is about 278.4071677937.

The spelling of 21579493 in words is "twenty-one million, five hundred seventy-nine thousand, four hundred ninety-three".