31559981 has 2 divisors, whose sum is σ = 31559982. Its totient is φ = 31559980.

The previous prime is 31559977. The next prime is 31559989. The reversal of 31559981 is 18995513.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27984100 + 3575881 = 5290^2 + 1891^2 .

It is an emirp because it is prime and its reverse (18995513) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31559981 - 2² = 31559977 is a prime.

It is a super-2 number, since 2×31559981² = 1992064801440722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31559989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15779990 + 15779991.

It is an arithmetic number, because the mean of its divisors is an integer number (15779991).

Almost surely, 2^31559981 is an apocalyptic number.

It is an amenable number.

31559981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31559981 is an equidigital number, since it uses as much as digits as its factorization.

31559981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48600, while the sum is 41.

The square root of 31559981 is about 5617.8270710302. The cubic root of 31559981 is about 316.0183086385.

The spelling of 31559981 in words is "thirty-one million, five hundred fifty-nine thousand, nine hundred eighty-one".