81661736 has 32 divisors (see below), whose sum is σ = 165480840. Its totient is φ = 37555968.

The previous prime is 81661733. The next prime is 81661739. The reversal of 81661736 is 63716618.

It is an interprime number because it is at equal distance from previous prime (81661733) and next prime (81661739).

It can be written as a sum of positive squares in 4 ways, for example, as 34739236 + 46922500 = 5894^2 + 6850^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81661736.

It is not an unprimeable number, because it can be changed into a prime (81661733) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31730 + ... + 34206.

Almost surely, 2^81661736 is an apocalyptic number.

It is an amenable number.

81661736 is an abundant number, since it is smaller than the sum of its proper divisors (83819104).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81661736 is a wasteful number, since it uses less digits than its factorization.

81661736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2813 (or 2809 counting only the distinct ones).

The product of its digits is 36288, while the sum is 38.

The square root of 81661736 is about 9036.6883314630. The cubic root of 81661736 is about 433.8499343136.

The spelling of 81661736 in words is "eighty-one million, six hundred sixty-one thousand, seven hundred thirty-six".