81687633012 has 18 divisors (see below), whose sum is σ = 206488183538. Its totient is φ = 27229210992.

The previous prime is 81687632963. The next prime is 81687633023. The reversal of 81687633012 is 21033678618.

81687633012 is a `hidden beast` number, since 8 + 1 + 6 + 8 + 7 + 633 + 0 + 1 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 72880561296 + 8807071716 = 269964^2 + 93846^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1134550423 + ... + 1134550494.

Almost surely, 2^81687633012 is an apocalyptic number.

It is an amenable number.

81687633012 is an abundant number, since it is smaller than the sum of its proper divisors (124800550526).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81687633012 is a wasteful number, since it uses less digits than its factorization.

81687633012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2269100927 (or 2269100922 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 81687633012 in words is "eighty-one billion, six hundred eighty-seven million, six hundred thirty-three thousand, twelve".