81712991 has 2 divisors, whose sum is σ = 81712992. Its totient is φ = 81712990.

The previous prime is 81712937. The next prime is 81713063. The reversal of 81712991 is 19921718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81712991 - 2¹⁰ = 81711967 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81712921) 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, 40856495 + 40856496.

It is an arithmetic number, because the mean of its divisors is an integer number (40856496).

Almost surely, 2^81712991 is an apocalyptic number.

81712991 is a deficient number, since it is larger than the sum of its proper divisors (1).

81712991 is an equidigital number, since it uses as much as digits as its factorization.

81712991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 38.

The square root of 81712991 is about 9039.5238259546. The cubic root of 81712991 is about 433.9406839872.

The spelling of 81712991 in words is "eighty-one million, seven hundred twelve thousand, nine hundred ninety-one".