81593108981 has 4 divisors (see below), whose sum is σ = 81611420172. Its totient is φ = 81574797792.

The previous prime is 81593108969. The next prime is 81593109029. The reversal of 81593108981 is 18980139518.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18980139518 = 2 ⋅9490069759.

It can be written as a sum of positive squares in 2 ways, for example, as 55821622756 + 25771486225 = 236266^2 + 160535^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81593108981 is a prime.

It is a super-2 number, since 2×81593108981² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81593108911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9148910 + ... + 9157823.

It is an arithmetic number, because the mean of its divisors is an integer number (20402855043).

Almost surely, 2^81593108981 is an apocalyptic number.

It is an amenable number.

81593108981 is a deficient number, since it is larger than the sum of its proper divisors (18311191).

81593108981 is a wasteful number, since it uses less digits than its factorization.

81593108981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18311190.

The product of its (nonzero) digits is 622080, while the sum is 53.

The spelling of 81593108981 in words is "eighty-one billion, five hundred ninety-three million, one hundred eight thousand, nine hundred eighty-one".