81681855208 has 16 divisors (see below), whose sum is σ = 153999633060. Its totient is φ = 40615286400.

The previous prime is 81681855191. The next prime is 81681855217. The reversal of 81681855208 is 80255818618.

It can be written as a sum of positive squares in 2 ways, for example, as 49071996484 + 32609858724 = 221522^2 + 180582^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28203613 + ... + 28206508.

Almost surely, 2^81681855208 is an apocalyptic number.

It is an amenable number.

81681855208 is a deficient number, since it is larger than the sum of its proper divisors (72317777852).

81681855208 is a wasteful number, since it uses less digits than its factorization.

81681855208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56410308 (or 56410304 counting only the distinct ones).

The product of its (nonzero) digits is 1228800, while the sum is 52.

The spelling of 81681855208 in words is "eighty-one billion, six hundred eighty-one million, eight hundred fifty-five thousand, two hundred eight".