81749674561 has 9 divisors (see below), whose sum is σ = 82390220899. Its totient is φ = 81114076624.

The previous prime is 81749674549. The next prime is 81749674603. The reversal of 81749674561 is 16547694718.

The square root of 81749674561 is 285919.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 48020148225 + 33729526336 = 219135^2 + 183656^2 .

It is not a de Polignac number, because 81749674561 - 2⁵ = 81749674529 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81749674496 and 81749674505.

It is not an unprimeable number, because it can be changed into a prime (81749674261) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 39169860 + ... + 39171946.

Almost surely, 2^81749674561 is an apocalyptic number.

81749674561 is the 285919-th square number.

81749674561 is the 142960-th centered octagonal number.

It is an amenable number.

81749674561 is a deficient number, since it is larger than the sum of its proper divisors (640546338).

81749674561 is an frugal number, since it uses more digits than its factorization.

81749674561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4448 (or 2224 counting only the distinct ones).

The product of its digits is 10160640, while the sum is 58.

The spelling of 81749674561 in words is "eighty-one billion, seven hundred forty-nine million, six hundred seventy-four thousand, five hundred sixty-one".