81665180 has 24 divisors (see below), whose sum is σ = 178954272. Its totient is φ = 31245632.

The previous prime is 81665167. The next prime is 81665183. The reversal of 81665180 is 8156618.

It is a self number, because there is not a number n which added to its sum of digits gives 81665180.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81665183) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88307 + ... + 89226.

It is an arithmetic number, because the mean of its divisors is an integer number (7456428).

Almost surely, 2^81665180 is an apocalyptic number.

It is an amenable number.

81665180 is an abundant number, since it is smaller than the sum of its proper divisors (97289092).

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

81665180 is a wasteful number, since it uses less digits than its factorization.

81665180 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177565 (or 177563 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 81665180 is about 9036.8788859871. The cubic root of 81665180 is about 433.8560332866.

The spelling of 81665180 in words is "eighty-one million, six hundred sixty-five thousand, one hundred eighty".