81111800 has 192 divisors, whose sum is σ = 246412800. Its totient is φ = 24076800.

The previous prime is 81111799. The next prime is 81111853. The reversal of 81111800 is 811118.

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

It is a congruent number.

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, 354086 + ... + 354314.

It is an arithmetic number, because the mean of its divisors is an integer number (1283400).

Almost surely, 2^81111800 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 81111800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123206400).

81111800 is an abundant number, since it is smaller than the sum of its proper divisors (165301000).

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

81111800 is a wasteful number, since it uses less digits than its factorization.

81111800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 286 (or 277 counting only the distinct ones).

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

The square root of 81111800 is about 9006.2089693722. The cubic root of 81111800 is about 432.8738456274.

Adding to 81111800 its reverse (811118), we get a palindrome (81922918).

Multiplying 81111800 by its reverse (811118), we get a square (65791240992400 = 8111180²).

81111800 divided by its reverse (811118) gives a square (100 = 10²).

The spelling of 81111800 in words is "eighty-one million, one hundred eleven thousand, eight hundred".