31619981 has 2 divisors, whose sum is σ = 31619982. Its totient is φ = 31619980.

The previous prime is 31619953. The next prime is 31619989. The reversal of 31619981 is 18991613.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16728100 + 14891881 = 4090^2 + 3859^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31619981 is a prime.

It is a super-3 number, since 3×31619981³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31619989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15809990 + 15809991.

It is an arithmetic number, because the mean of its divisors is an integer number (15809991).

Almost surely, 2^31619981 is an apocalyptic number.

It is an amenable number.

31619981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31619981 is an equidigital number, since it uses as much as digits as its factorization.

31619981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11664, while the sum is 38.

The square root of 31619981 is about 5623.1646783640. The cubic root of 31619981 is about 316.2184470699.

The spelling of 31619981 in words is "thirty-one million, six hundred nineteen thousand, nine hundred eighty-one".