81191880 has 384 divisors, whose sum is σ = 343699200. Its totient is φ = 16128000.

The previous prime is 81191867. The next prime is 81191897. The reversal of 81191880 is 8819118.

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

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 803830 + ... + 803930.

It is an arithmetic number, because the mean of its divisors is an integer number (895050).

Almost surely, 2^81191880 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 81191880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (171849600).

81191880 is an abundant number, since it is smaller than the sum of its proper divisors (262507320).

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

81191880 is a wasteful number, since it uses less digits than its factorization.

81191880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165 (or 158 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 36.

The square root of 81191880 is about 9010.6536943776. The cubic root of 81191880 is about 433.0162545657.

It can be divided in two parts, 8119 and 1880, that added together give a palindrome (9999).

The spelling of 81191880 in words is "eighty-one million, one hundred ninety-one thousand, eight hundred eighty".