31681231 has 2 divisors, whose sum is σ = 31681232. Its totient is φ = 31681230.

The previous prime is 31681229. The next prime is 31681261. The reversal of 31681231 is 13218613.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31681231 - 2¹ = 31681229 is a prime.

It is a super-2 number, since 2×31681231² = 2007400795350722, which contains 22 as substring.

Together with 31681229, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 31681196 and 31681205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31681261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15840615 + 15840616.

It is an arithmetic number, because the mean of its divisors is an integer number (15840616).

Almost surely, 2^31681231 is an apocalyptic number.

31681231 is a deficient number, since it is larger than the sum of its proper divisors (1).

31681231 is an equidigital number, since it uses as much as digits as its factorization.

31681231 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 25.

The square root of 31681231 is about 5628.6082649266. The cubic root of 31681231 is about 316.4224940762.

Adding to 31681231 its reverse (13218613), we get a palindrome (44899844).

The spelling of 31681231 in words is "thirty-one million, six hundred eighty-one thousand, two hundred thirty-one".