918631981 has 2 divisors, whose sum is σ = 918631982. Its totient is φ = 918631980.

The previous prime is 918631877. The next prime is 918632003. The reversal of 918631981 is 189136819.

It is a happy number.

918631981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 916575625 + 2056356 = 30275^2 + 1434^2 .

It is a cyclic number.

It is not a de Polignac number, because 918631981 - 2⁷ = 918631853 is a prime.

It is a super-2 number, since 2×918631981² = 1687769433031968722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (918671981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 459315990 + 459315991.

It is an arithmetic number, because the mean of its divisors is an integer number (459315991).

Almost surely, 2^918631981 is an apocalyptic number.

It is an amenable number.

918631981 is a deficient number, since it is larger than the sum of its proper divisors (1).

918631981 is an equidigital number, since it uses as much as digits as its factorization.

918631981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 93312, while the sum is 46.

The square root of 918631981 is about 30308.9422613195. The cubic root of 918631981 is about 972.1065146163.

The spelling of 918631981 in words is "nine hundred eighteen million, six hundred thirty-one thousand, nine hundred eighty-one".