81351696581 has 2 divisors, whose sum is σ = 81351696582. Its totient is φ = 81351696580.

The previous prime is 81351696539. The next prime is 81351696637. The reversal of 81351696581 is 18569615318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77070088225 + 4281608356 = 277615^2 + 65434^2 .

It is a cyclic number.

It is not a de Polignac number, because 81351696581 - 2²² = 81347502277 is a prime.

It is a super-2 number, since 2×81351696581² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81351896581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40675848290 + 40675848291.

It is an arithmetic number, because the mean of its divisors is an integer number (40675848291).

Almost surely, 2^81351696581 is an apocalyptic number.

It is an amenable number.

81351696581 is a deficient number, since it is larger than the sum of its proper divisors (1).

81351696581 is an equidigital number, since it uses as much as digits as its factorization.

81351696581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1555200, while the sum is 53.

The spelling of 81351696581 in words is "eighty-one billion, three hundred fifty-one million, six hundred ninety-six thousand, five hundred eighty-one".