31661681 has 2 divisors, whose sum is σ = 31661682. Its totient is φ = 31661680.

The previous prime is 31661611. The next prime is 31661689. The reversal of 31661681 is 18616613.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25411681 + 6250000 = 5041^2 + 2500^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31661681 is a prime.

It is a super-2 number, since 2×31661681² = 2004924087491522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31661689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15830840 + 15830841.

It is an arithmetic number, because the mean of its divisors is an integer number (15830841).

Almost surely, 2^31661681 is an apocalyptic number.

It is an amenable number.

31661681 is a deficient number, since it is larger than the sum of its proper divisors (1).

31661681 is an equidigital number, since it uses as much as digits as its factorization.

31661681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 32.

The square root of 31661681 is about 5626.8713331655. The cubic root of 31661681 is about 316.3573942001.

The spelling of 31661681 in words is "thirty-one million, six hundred sixty-one thousand, six hundred eighty-one".