81707828644 has 18 divisors (see below), whose sum is σ = 154833919170. Its totient is φ = 37711305216.

The previous prime is 81707828621. The next prime is 81707828659. The reversal of 81707828644 is 44682870718.

It can be written as a sum of positive squares in 3 ways, for example, as 11212268544 + 70495560100 = 105888^2 + 265510^2 .

It is a super-3 number, since 3×81707828644³ (a number of 34 digits) contains 333 as substring.

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, 60434109 + ... + 60435460.

Almost surely, 2^81707828644 is an apocalyptic number.

It is an amenable number.

81707828644 is a deficient number, since it is larger than the sum of its proper divisors (73126090526).

81707828644 is a wasteful number, since it uses less digits than its factorization.

81707828644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120869599 (or 120869584 counting only the distinct ones).

The product of its (nonzero) digits is 4816896, while the sum is 55.

The spelling of 81707828644 in words is "eighty-one billion, seven hundred seven million, eight hundred twenty-eight thousand, six hundred forty-four".