81518855554 has 4 divisors (see below), whose sum is σ = 122278283334. Its totient is φ = 40759427776.

The previous prime is 81518855393. The next prime is 81518855563. The reversal of 81518855554 is 45555881518.

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

It can be written as a sum of positive squares in only one way, i.e., 47425079529 + 34093776025 = 217773^2 + 184645^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81518855495 and 81518855504.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20379713887 + ... + 20379713890.

Almost surely, 2^81518855554 is an apocalyptic number.

81518855554 is a deficient number, since it is larger than the sum of its proper divisors (40759427780).

81518855554 is a wasteful number, since it uses less digits than its factorization.

81518855554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40759427779.

The product of its digits is 6400000, while the sum is 55.

The spelling of 81518855554 in words is "eighty-one billion, five hundred eighteen million, eight hundred fifty-five thousand, five hundred fifty-four".