31481981 has 2 divisors, whose sum is σ = 31481982. Its totient is φ = 31481980.

The previous prime is 31481951. The next prime is 31482013. The reversal of 31481981 is 18918413.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28622500 + 2859481 = 5350^2 + 1691^2 .

It is an emirp because it is prime and its reverse (18918413) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31481981 is a prime.

It is a super-2 number, since 2×31481981² = 1982230255368722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31481911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15740990 + 15740991.

It is an arithmetic number, because the mean of its divisors is an integer number (15740991).

Almost surely, 2^31481981 is an apocalyptic number.

It is an amenable number.

31481981 is a deficient number, since it is larger than the sum of its proper divisors (1).

31481981 is an equidigital number, since it uses as much as digits as its factorization.

31481981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 35.

The square root of 31481981 is about 5610.8805904243. The cubic root of 31481981 is about 315.7577490932.

The spelling of 31481981 in words is "thirty-one million, four hundred eighty-one thousand, nine hundred eighty-one".