81181627920 has 200 divisors, whose sum is σ = 291679110360. Its totient is φ = 20901888000.

The previous prime is 81181627907. The next prime is 81181627927. The reversal of 81181627920 is 2972618118.

81181627920 is a `hidden beast` number, since 8 + 1 + 18 + 1 + 627 + 9 + 2 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 52359696 + 81129268224 = 7236^2 + 284832^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (81181627927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 28081 + ... + 403920.

Almost surely, 2^81181627920 is an apocalyptic number.

81181627920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81181627920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (145839555180).

81181627920 is an abundant number, since it is smaller than the sum of its proper divisors (210497482440).

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

81181627920 is a wasteful number, since it uses less digits than its factorization.

81181627920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 432055 (or 432040 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 45.

The spelling of 81181627920 in words is "eighty-one billion, one hundred eighty-one million, six hundred twenty-seven thousand, nine hundred twenty".