231513021 has 24 divisors (see below), whose sum is σ = 355922424. Its totient is φ = 144506880.

The previous prime is 231513017. The next prime is 231513031. The reversal of 231513021 is 120315132.

It can be written as a sum of positive squares in 4 ways, for example, as 156500100 + 75012921 = 12510^2 + 8661^2 .

It is not a de Polignac number, because 231513021 - 2² = 231513017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 231512985 and 231513003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231513031) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26301 + ... + 33981.

It is an arithmetic number, because the mean of its divisors is an integer number (14830101).

Almost surely, 2^231513021 is an apocalyptic number.

It is an amenable number.

231513021 is a deficient number, since it is larger than the sum of its proper divisors (124409403).

231513021 is a wasteful number, since it uses less digits than its factorization.

231513021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7901 (or 7898 counting only the distinct ones).

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

The square root of 231513021 is about 15215.5519452960. The cubic root of 231513021 is about 614.0331347261.

Adding to 231513021 its reverse (120315132), we get a palindrome (351828153).

The spelling of 231513021 in words is "two hundred thirty-one million, five hundred thirteen thousand, twenty-one".