81718519 has 2 divisors, whose sum is σ = 81718520. Its totient is φ = 81718518.

The previous prime is 81718513. The next prime is 81718529. The reversal of 81718519 is 91581718.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81718519 is a prime.

It is a super-2 number, since 2×81718519² = 13355832695106722, which contains 22 as substring.

It is equal to p_4763965 and since 81718519 and 4763965 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81718513) 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, 40859259 + 40859260.

It is an arithmetic number, because the mean of its divisors is an integer number (40859260).

Almost surely, 2^81718519 is an apocalyptic number.

81718519 is a deficient number, since it is larger than the sum of its proper divisors (1).

81718519 is an equidigital number, since it uses as much as digits as its factorization.

81718519 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 40.

The square root of 81718519 is about 9039.8295891018. The cubic root of 81718519 is about 433.9504693346.

The spelling of 81718519 in words is "eighty-one million, seven hundred eighteen thousand, five hundred nineteen".