81637704 has 24 divisors (see below), whose sum is σ = 221102310. Its totient is φ = 27212544.

The previous prime is 81637687. The next prime is 81637709. The reversal of 81637704 is 40773618.

It can be written as a sum of positive squares in only one way, i.e., 57608100 + 24029604 = 7590^2 + 4902^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81637709) 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 5 ways as a sum of consecutive naturals, for example, 566857 + ... + 567000.

Almost surely, 2^81637704 is an apocalyptic number.

It is an amenable number.

81637704 is an abundant number, since it is smaller than the sum of its proper divisors (139464606).

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

81637704 is a wasteful number, since it uses less digits than its factorization.

81637704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133869 (or 1133862 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 36.

The square root of 81637704 is about 9035.3585429688. The cubic root of 81637704 is about 433.8073713171.

The spelling of 81637704 in words is "eighty-one million, six hundred thirty-seven thousand, seven hundred four".