231720431 has 2 divisors, whose sum is σ = 231720432. Its totient is φ = 231720430.

The previous prime is 231720413. The next prime is 231720493. The reversal of 231720431 is 134027132.

Together with previous prime (231720413) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 231720431 - 2¹⁰ = 231719407 is a prime.

It is a super-3 number, since 3×231720431³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Sophie Germain prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 231720397 and 231720406.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231726431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115860215 + 115860216.

It is an arithmetic number, because the mean of its divisors is an integer number (115860216).

Almost surely, 2^231720431 is an apocalyptic number.

231720431 is a deficient number, since it is larger than the sum of its proper divisors (1).

231720431 is an equidigital number, since it uses as much as digits as its factorization.

231720431 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 231720431 is about 15222.3661432775. The cubic root of 231720431 is about 614.2164485319.

Adding to 231720431 its reverse (134027132), we get a palindrome (365747563).

The spelling of 231720431 in words is "two hundred thirty-one million, seven hundred twenty thousand, four hundred thirty-one".