31686989 has 2 divisors, whose sum is σ = 31686990. Its totient is φ = 31686988.

The previous prime is 31686983. The next prime is 31687013. The reversal of 31686989 is 98968613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24304900 + 7382089 = 4930^2 + 2717^2 .

It is an emirp because it is prime and its reverse (98968613) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31686989 is a prime.

It is a super-2 number, since 2×31686989² = 2008130543772242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31686983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15843494 + 15843495.

It is an arithmetic number, because the mean of its divisors is an integer number (15843495).

Almost surely, 2^31686989 is an apocalyptic number.

It is an amenable number.

31686989 is a deficient number, since it is larger than the sum of its proper divisors (1).

31686989 is an equidigital number, since it uses as much as digits as its factorization.

31686989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 559872, while the sum is 50.

The square root of 31686989 is about 5629.1197358024. The cubic root of 31686989 is about 316.4416626322.

The spelling of 31686989 in words is "thirty-one million, six hundred eighty-six thousand, nine hundred eighty-nine".