311981 has 2 divisors, whose sum is σ = 311982. Its totient is φ = 311980.

The previous prime is 311963. The next prime is 312007. The reversal of 311981 is 189113.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 259081 + 52900 = 509^2 + 230^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-311981 is a prime.

It is a super-2 number, since 2×311981² = 194664288722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 311981.

It is not a weakly prime, because it can be changed into another prime (311951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155990 + 155991.

It is an arithmetic number, because the mean of its divisors is an integer number (155991).

2³¹¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

311981 is a deficient number, since it is larger than the sum of its proper divisors (1).

311981 is an equidigital number, since it uses as much as digits as its factorization.

311981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 216, while the sum is 23.

The square root of 311981 is about 558.5525937636. The cubic root of 311981 is about 67.8228520585.

The spelling of 311981 in words is "three hundred eleven thousand, nine hundred eighty-one".