81917039 has 2 divisors, whose sum is σ = 81917040. Its totient is φ = 81917038.

The previous prime is 81916997. The next prime is 81917041. The reversal of 81917039 is 93071918.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81917039 is a prime.

Together with 81917041, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_4774835 and since 81917039 and 4774835 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 81916993 and 81917011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81917639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40958519 + 40958520.

It is an arithmetic number, because the mean of its divisors is an integer number (40958520).

Almost surely, 2^81917039 is an apocalyptic number.

81917039 is a deficient number, since it is larger than the sum of its proper divisors (1).

81917039 is an equidigital number, since it uses as much as digits as its factorization.

81917039 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13608, while the sum is 38.

The square root of 81917039 is about 9050.8032240238. The cubic root of 81917039 is about 434.3015859160.

The spelling of 81917039 in words is "eighty-one million, nine hundred seventeen thousand, thirty-nine".