81375278681 has 4 divisors (see below), whose sum is σ = 81564084864. Its totient is φ = 81186472500.

The previous prime is 81375278627. The next prime is 81375278707. The reversal of 81375278681 is 18687257318.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81375278681 is a prime.

It is a super-2 number, since 2×81375278681² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81375278981) 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, 94402445 + ... + 94403306.

It is an arithmetic number, because the mean of its divisors is an integer number (20391021216).

Almost surely, 2^81375278681 is an apocalyptic number.

It is an amenable number.

81375278681 is a deficient number, since it is larger than the sum of its proper divisors (188806183).

81375278681 is a wasteful number, since it uses less digits than its factorization.

81375278681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188806182.

The product of its digits is 4515840, while the sum is 56.

The spelling of 81375278681 in words is "eighty-one billion, three hundred seventy-five million, two hundred seventy-eight thousand, six hundred eighty-one".