81726660 has 72 divisors (see below), whose sum is σ = 253693440. Its totient is φ = 21284928.

The previous prime is 81726637. The next prime is 81726661. The reversal of 81726660 is 6662718.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81726661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2461 + ... + 13019.

It is an arithmetic number, because the mean of its divisors is an integer number (3523520).

Almost surely, 2^81726660 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 81726660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126846720).

81726660 is an abundant number, since it is smaller than the sum of its proper divisors (171966780).

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

81726660 is a wasteful number, since it uses less digits than its factorization.

81726660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10617 (or 10612 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 81726660 is about 9040.2798629246. The cubic root of 81726660 is about 433.9648792607.

The spelling of 81726660 in words is "eighty-one million, seven hundred twenty-six thousand, six hundred sixty".