21539313 has 6 divisors (see below), whose sum is σ = 31112354. Its totient is φ = 14359536.

The previous prime is 21539311. The next prime is 21539321. The reversal of 21539313 is 31393512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 12194064 + 9345249 = 3492^2 + 3057^2 .

It is not a de Polignac number, because 21539313 - 2¹ = 21539311 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21539311) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196620 + ... + 1196637.

Almost surely, 2^21539313 is an apocalyptic number.

It is an amenable number.

21539313 is a deficient number, since it is larger than the sum of its proper divisors (9573041).

21539313 is a wasteful number, since it uses less digits than its factorization.

21539313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2393263 (or 2393260 counting only the distinct ones).

The product of its digits is 2430, while the sum is 27.

The square root of 21539313 is about 4641.0465414602. The cubic root of 21539313 is about 278.2342667584.

The spelling of 21539313 in words is "twenty-one million, five hundred thirty-nine thousand, three hundred thirteen".