81185188 has 48 divisors (see below), whose sum is σ = 166852224. Its totient is φ = 33845760.

The previous prime is 81185179. The next prime is 81185191. The reversal of 81185188 is 88158118.

It is a self number, because there is not a number n which added to its sum of digits gives 81185188.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 336748 + ... + 336988.

It is an arithmetic number, because the mean of its divisors is an integer number (3476088).

Almost surely, 2^81185188 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81185188, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (83426112).

81185188 is an abundant number, since it is smaller than the sum of its proper divisors (85667036).

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

81185188 is a wasteful number, since it uses less digits than its factorization.

81185188 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532 (or 530 counting only the distinct ones).

The product of its digits is 20480, while the sum is 40.

The square root of 81185188 is about 9010.2823485172. The cubic root of 81185188 is about 433.0043575451.

The spelling of 81185188 in words is "eighty-one million, one hundred eighty-five thousand, one hundred eighty-eight".