81975559 has 2 divisors, whose sum is σ = 81975560. Its totient is φ = 81975558.

The previous prime is 81975541. The next prime is 81975571. The reversal of 81975559 is 95557918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81975559 - 2²³ = 73586951 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81975659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40987779 + 40987780.

It is an arithmetic number, because the mean of its divisors is an integer number (40987780).

Almost surely, 2^81975559 is an apocalyptic number.

81975559 is a deficient number, since it is larger than the sum of its proper divisors (1).

81975559 is an equidigital number, since it uses as much as digits as its factorization.

81975559 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 567000, while the sum is 49.

The square root of 81975559 is about 9054.0355090976. The cubic root of 81975559 is about 434.4049802746.

The spelling of 81975559 in words is "eighty-one million, nine hundred seventy-five thousand, five hundred fifty-nine".