81671218612 has 6 divisors (see below), whose sum is σ = 142924632578. Its totient is φ = 40835609304.

The previous prime is 81671218543. The next prime is 81671218649. The reversal of 81671218612 is 21681217618.

It can be written as a sum of positive squares in only one way, i.e., 77236191396 + 4435027216 = 277914^2 + 66596^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10208902323 + ... + 10208902330.

Almost surely, 2^81671218612 is an apocalyptic number.

It is an amenable number.

81671218612 is a deficient number, since it is larger than the sum of its proper divisors (61253413966).

81671218612 is a wasteful number, since it uses less digits than its factorization.

81671218612 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20417804657 (or 20417804655 counting only the distinct ones).

The product of its digits is 64512, while the sum is 43.

The spelling of 81671218612 in words is "eighty-one billion, six hundred seventy-one million, two hundred eighteen thousand, six hundred twelve".