81681773216 has 12 divisors (see below), whose sum is σ = 160810991082. Its totient is φ = 40840886592.

The previous prime is 81681773209. The next prime is 81681773269. The reversal of 81681773216 is 61237718618.

It can be written as a sum of positive squares in only one way, i.e., 70116921616 + 11564851600 = 264796^2 + 107540^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1276277675 + ... + 1276277738.

Almost surely, 2^81681773216 is an apocalyptic number.

It is an amenable number.

81681773216 is a deficient number, since it is larger than the sum of its proper divisors (79129217866).

81681773216 is a wasteful number, since it uses less digits than its factorization.

81681773216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2552555423 (or 2552555415 counting only the distinct ones).

The product of its digits is 677376, while the sum is 50.

The spelling of 81681773216 in words is "eighty-one billion, six hundred eighty-one million, seven hundred seventy-three thousand, two hundred sixteen".