81969159817 has 2 divisors, whose sum is σ = 81969159818. Its totient is φ = 81969159816.

The previous prime is 81969159773. The next prime is 81969159821. The reversal of 81969159817 is 71895196918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81949940361 + 19219456 = 286269^2 + 4384^2 .

It is a cyclic number.

It is not a de Polignac number, because 81969159817 - 2⁷ = 81969159689 is a prime.

It is a super-2 number, since 2×81969159817² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81969159847) 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, 40984579908 + 40984579909.

It is an arithmetic number, because the mean of its divisors is an integer number (40984579909).

Almost surely, 2^81969159817 is an apocalyptic number.

It is an amenable number.

81969159817 is a deficient number, since it is larger than the sum of its proper divisors (1).

81969159817 is an equidigital number, since it uses as much as digits as its factorization.

81969159817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9797760, while the sum is 64.

The spelling of 81969159817 in words is "eighty-one billion, nine hundred sixty-nine million, one hundred fifty-nine thousand, eight hundred seventeen".