81180100 has 81 divisors (see below), whose sum is σ = 190730197. Its totient is φ = 29985280.

The previous prime is 81180097. The next prime is 81180101. The reversal of 81180100 is 108118.

81180100 = 25² + 26² + ... + 624².

The square root of 81180100 is 9010.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 12489156 + 68690944 = 3534^2 + 8288^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81180101) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1531674 + ... + 1531726.

Almost surely, 2^81180100 is an apocalyptic number.

81180100 is the 9010-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81180100

81180100 is an abundant number, since it is smaller than the sum of its proper divisors (109550097).

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

81180100 is a wasteful number, since it uses less digits than its factorization.

81180100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 77 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 19.

The cubic root of 81180100 is about 432.9953116742.

Multiplying 81180100 by its product of nonzero digits (64), we get a square (5195526400 = 72080²).

Adding to 81180100 its reverse (108118), we get a palindrome (81288218).

The spelling of 81180100 in words is "eighty-one million, one hundred eighty thousand, one hundred".