81811700 has 36 divisors (see below), whose sum is σ = 178595340. Its totient is φ = 32528640.

The previous prime is 81811657. The next prime is 81811703. The reversal of 81811700 is 711818.

It can be written as a sum of positive squares in 6 ways, for example, as 3984016 + 77827684 = 1996^2 + 8822^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81811700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81811703) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14936 + ... + 19664.

Almost surely, 2^81811700 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 81811700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89297670).

81811700 is an abundant number, since it is smaller than the sum of its proper divisors (96783640).

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

81811700 is a wasteful number, since it uses less digits than its factorization.

81811700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4916 (or 4909 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 26.

The square root of 81811700 is about 9044.9820342552. The cubic root of 81811700 is about 434.1153466053.

The spelling of 81811700 in words is "eighty-one million, eight hundred eleven thousand, seven hundred".