21231513 has 12 divisors (see below), whose sum is σ = 30972708. Its totient is φ = 14013600.

The previous prime is 21231503. The next prime is 21231523. The reversal of 21231513 is 31513212.

It is an interprime number because it is at equal distance from previous prime (21231503) and next prime (21231523).

It can be written as a sum of positive squares in 2 ways, for example, as 19079424 + 2152089 = 4368^2 + 1467^2 .

It is not a de Polignac number, because 21231513 - 2⁶ = 21231449 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21231503) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10770 + ... + 12587.

It is an arithmetic number, because the mean of its divisors is an integer number (2581059).

Almost surely, 2^21231513 is an apocalyptic number.

It is an amenable number.

21231513 is a deficient number, since it is larger than the sum of its proper divisors (9741195).

21231513 is a wasteful number, since it uses less digits than its factorization.

21231513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23464 (or 23461 counting only the distinct ones).

The product of its digits is 180, while the sum is 18.

The square root of 21231513 is about 4607.7665956513. The cubic root of 21231513 is about 276.9025666611.

Adding to 21231513 its reverse (31513212), we get a palindrome (52744725).

The spelling of 21231513 in words is "twenty-one million, two hundred thirty-one thousand, five hundred thirteen".