81171832720 has 160 divisors (see below), whose sum is σ = 211758053760. Its totient is φ = 28681605120.

The previous prime is 81171832711. The next prime is 81171832733. The reversal of 81171832720 is 2723817118.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7449036 + ... + 7459924.

It is an arithmetic number, because the mean of its divisors is an integer number (1323487836).

Almost surely, 2^81171832720 is an apocalyptic number.

81171832720 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 81171832720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105879026880).

81171832720 is an abundant number, since it is smaller than the sum of its proper divisors (130586221040).

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

81171832720 is a wasteful number, since it uses less digits than its factorization.

81171832720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11153 (or 11147 counting only the distinct ones).

The product of its (nonzero) digits is 37632, while the sum is 40.

The spelling of 81171832720 in words is "eighty-one billion, one hundred seventy-one million, eight hundred thirty-two thousand, seven hundred twenty".