81078917 has 2 divisors, whose sum is σ = 81078918. Its totient is φ = 81078916.

The previous prime is 81078889. The next prime is 81078953. The reversal of 81078917 is 71987018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54184321 + 26894596 = 7361^2 + 5186^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81078917 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81078317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40539458 + 40539459.

It is an arithmetic number, because the mean of its divisors is an integer number (40539459).

Almost surely, 2^81078917 is an apocalyptic number.

It is an amenable number.

81078917 is a deficient number, since it is larger than the sum of its proper divisors (1).

81078917 is an equidigital number, since it uses as much as digits as its factorization.

81078917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28224, while the sum is 41.

The square root of 81078917 is about 9004.3832104148. The cubic root of 81078917 is about 432.8153415436.

The spelling of 81078917 in words is "eighty-one million, seventy-eight thousand, nine hundred seventeen".