315981781 has 2 divisors, whose sum is σ = 315981782. Its totient is φ = 315981780.

The previous prime is 315981749. The next prime is 315981817. The reversal of 315981781 is 187189513.

Together with next prime (315981817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 310076881 + 5904900 = 17609^2 + 2430^2 .

It is a cyclic number.

It is not a de Polignac number, because 315981781 - 2⁵ = 315981749 is a prime.

It is a super-2 number, since 2×315981781² = 199688971847863922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (315981181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 157990890 + 157990891.

It is an arithmetic number, because the mean of its divisors is an integer number (157990891).

Almost surely, 2^315981781 is an apocalyptic number.

It is an amenable number.

315981781 is a deficient number, since it is larger than the sum of its proper divisors (1).

315981781 is an equidigital number, since it uses as much as digits as its factorization.

315981781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 43.

The square root of 315981781 is about 17775.8763778330. The cubic root of 315981781 is about 681.1153703492.

The spelling of 315981781 in words is "three hundred fifteen million, nine hundred eighty-one thousand, seven hundred eighty-one".