81759681 has 24 divisors (see below), whose sum is σ = 126177480. Its totient is φ = 50835456.

The previous prime is 81759611. The next prime is 81759683. The reversal of 81759681 is 18695718.

It can be written as a sum of positive squares in 4 ways, for example, as 921600 + 80838081 = 960^2 + 8991^2 .

It is not a de Polignac number, because 81759681 - 2¹³ = 81751489 is a prime.

It is a super-2 number, since 2×81759681² = 13369290874443522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81759683) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14925 + ... + 19653.

It is an arithmetic number, because the mean of its divisors is an integer number (5257395).

Almost surely, 2^81759681 is an apocalyptic number.

It is an amenable number.

81759681 is a deficient number, since it is larger than the sum of its proper divisors (44417799).

81759681 is a wasteful number, since it uses less digits than its factorization.

81759681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4865 (or 4862 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81759681 is about 9042.1060046872. The cubic root of 81759681 is about 434.0233180645.

The spelling of 81759681 in words is "eighty-one million, seven hundred fifty-nine thousand, six hundred eighty-one".