81181100 has 144 divisors (see below), whose sum is σ = 236818176. Its totient is φ = 23328000.

The previous prime is 81181081. The next prime is 81181117. The reversal of 81181100 is 118118.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 99695 + ... + 100505.

Almost surely, 2^81181100 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 81181100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118409088).

81181100 is an abundant number, since it is smaller than the sum of its proper divisors (155637076).

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

81181100 is a wasteful number, since it uses less digits than its factorization.

81181100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 856 (or 849 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 20.

The square root of 81181100 is about 9010.0554937248. The cubic root of 81181100 is about 432.9970895875.

Adding to 81181100 its reverse (118118), we get a palindrome (81299218).

It can be divided in two parts, 811 and 81100, that multiplied together give a square (65772100 = 8110²).

The spelling of 81181100 in words is "eighty-one million, one hundred eighty-one thousand, one hundred".