81666943 has 2 divisors, whose sum is σ = 81666944. Its totient is φ = 81666942.

The previous prime is 81666931. The next prime is 81666953. The reversal of 81666943 is 34966618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81666943 - 2⁵ = 81666911 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81666943.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81666953) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40833471 + 40833472.

It is an arithmetic number, because the mean of its divisors is an integer number (40833472).

Almost surely, 2^81666943 is an apocalyptic number.

81666943 is a deficient number, since it is larger than the sum of its proper divisors (1).

81666943 is an equidigital number, since it uses as much as digits as its factorization.

81666943 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 43.

The square root of 81666943 is about 9036.9764302005. The cubic root of 81666943 is about 433.8591553136.

The spelling of 81666943 in words is "eighty-one million, six hundred sixty-six thousand, nine hundred forty-three".