81990179 has 2 divisors, whose sum is σ = 81990180. Its totient is φ = 81990178.

The previous prime is 81990151. The next prime is 81990197. The reversal of 81990179 is 97109918.

Together with next prime (81990197) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81990179 is a prime.

It is not a weakly prime, because it can be changed into another prime (81990199) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40995089 + 40995090.

It is an arithmetic number, because the mean of its divisors is an integer number (40995090).

Almost surely, 2^81990179 is an apocalyptic number.

81990179 is a deficient number, since it is larger than the sum of its proper divisors (1).

81990179 is an equidigital number, since it uses as much as digits as its factorization.

81990179 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40824, while the sum is 44.

The square root of 81990179 is about 9054.8428478908. The cubic root of 81990179 is about 434.4308035134.

The spelling of 81990179 in words is "eighty-one million, nine hundred ninety thousand, one hundred seventy-nine".