81687256774 has 4 divisors (see below), whose sum is σ = 122530885164. Its totient is φ = 40843628386.

The previous prime is 81687256759. The next prime is 81687256787. The reversal of 81687256774 is 47765278618.

It is a semiprime because it is the product of two primes.

It is a super-2 number, since 2×81687256774² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20421814192 + ... + 20421814195.

It is an arithmetic number, because the mean of its divisors is an integer number (30632721291).

Almost surely, 2^81687256774 is an apocalyptic number.

81687256774 is a deficient number, since it is larger than the sum of its proper divisors (40843628390).

81687256774 is a wasteful number, since it uses less digits than its factorization.

81687256774 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40843628389.

The product of its digits is 31610880, while the sum is 61.

The spelling of 81687256774 in words is "eighty-one billion, six hundred eighty-seven million, two hundred fifty-six thousand, seven hundred seventy-four".