31891631 has 2 divisors, whose sum is σ = 31891632. Its totient is φ = 31891630.

The previous prime is 31891621. The next prime is 31891663. The reversal of 31891631 is 13619813.

It is an a-pointer prime, because the next prime (31891663) can be obtained adding 31891631 to its sum of digits (32).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31891631 - 2¹⁴ = 31875247 is a prime.

It is a super-2 number, since 2×31891631² = 2034152255680322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31891621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15945815 + 15945816.

It is an arithmetic number, because the mean of its divisors is an integer number (15945816).

Almost surely, 2^31891631 is an apocalyptic number.

31891631 is a deficient number, since it is larger than the sum of its proper divisors (1).

31891631 is an equidigital number, since it uses as much as digits as its factorization.

31891631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 32.

The square root of 31891631 is about 5647.2675693649. The cubic root of 31891631 is about 317.1214195182.

The spelling of 31891631 in words is "thirty-one million, eight hundred ninety-one thousand, six hundred thirty-one".