81600873581 has 2 divisors, whose sum is σ = 81600873582. Its totient is φ = 81600873580.

The previous prime is 81600873551. The next prime is 81600873617. The reversal of 81600873581 is 18537800618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77311802500 + 4289071081 = 278050^2 + 65491^2 .

It is a cyclic number.

It is not a de Polignac number, because 81600873581 - 2²² = 81596679277 is a prime.

It is a super-2 number, since 2×81600873581² (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 (81600873551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40800436790 + 40800436791.

It is an arithmetic number, because the mean of its divisors is an integer number (40800436791).

Almost surely, 2^81600873581 is an apocalyptic number.

It is an amenable number.

81600873581 is a deficient number, since it is larger than the sum of its proper divisors (1).

81600873581 is an equidigital number, since it uses as much as digits as its factorization.

81600873581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 322560, while the sum is 47.

The spelling of 81600873581 in words is "eighty-one billion, six hundred million, eight hundred seventy-three thousand, five hundred eighty-one".