81359917 has 2 divisors, whose sum is σ = 81359918. Its totient is φ = 81359916.

The previous prime is 81359899. The next prime is 81359921. The reversal of 81359917 is 71995318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78517321 + 2842596 = 8861^2 + 1686^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81359917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81359987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40679958 + 40679959.

It is an arithmetic number, because the mean of its divisors is an integer number (40679959).

Almost surely, 2^81359917 is an apocalyptic number.

It is an amenable number.

81359917 is a deficient number, since it is larger than the sum of its proper divisors (1).

81359917 is an equidigital number, since it uses as much as digits as its factorization.

81359917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 68040, while the sum is 43.

The square root of 81359917 is about 9019.9732261243. The cubic root of 81359917 is about 433.3147762599.

The spelling of 81359917 in words is "eighty-one million, three hundred fifty-nine thousand, nine hundred seventeen".