81388382857 has 4 divisors (see below), whose sum is σ = 81399620736. Its totient is φ = 81377144980.

The previous prime is 81388382807. The next prime is 81388382893. The reversal of 81388382857 is 75828388318.

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, and also an emirpimes, since its reverse is a distinct semiprime: 75828388318 = 2 ⋅37914194159.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81388382857 is a prime.

It is a super-2 number, since 2×81388382857² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81388382795 and 81388382804.

It is not an unprimeable number, because it can be changed into a prime (81388382807) 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, 5608069 + ... + 5622562.

It is an arithmetic number, because the mean of its divisors is an integer number (20349905184).

Almost surely, 2^81388382857 is an apocalyptic number.

It is an amenable number.

81388382857 is a deficient number, since it is larger than the sum of its proper divisors (11237879).

81388382857 is a wasteful number, since it uses less digits than its factorization.

81388382857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11237878.

The product of its digits is 20643840, while the sum is 61.

The spelling of 81388382857 in words is "eighty-one billion, three hundred eighty-eight million, three hundred eighty-two thousand, eight hundred fifty-seven".