81908645471 has 2 divisors, whose sum is σ = 81908645472. Its totient is φ = 81908645470.

The previous prime is 81908645411. The next prime is 81908645513. The reversal of 81908645471 is 17454680918.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81908645471 is a prime.

It is a super-3 number, since 3×81908645471³ (a number of 34 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81908645411) 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, 40954322735 + 40954322736.

It is an arithmetic number, because the mean of its divisors is an integer number (40954322736).

Almost surely, 2^81908645471 is an apocalyptic number.

81908645471 is a deficient number, since it is larger than the sum of its proper divisors (1).

81908645471 is an equidigital number, since it uses as much as digits as its factorization.

81908645471 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1935360, while the sum is 53.

The spelling of 81908645471 in words is "eighty-one billion, nine hundred eight million, six hundred forty-five thousand, four hundred seventy-one".