81721116 has 96 divisors (see below), whose sum is σ = 223534080. Its totient is φ = 25768512.

The previous prime is 81721103. The next prime is 81721121. The reversal of 81721116 is 61112718.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 81721116.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 414730 + ... + 414926.

It is an arithmetic number, because the mean of its divisors is an integer number (2328480).

Almost surely, 2^81721116 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 81721116, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111767040).

81721116 is an abundant number, since it is smaller than the sum of its proper divisors (141812964).

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

81721116 is a wasteful number, since it uses less digits than its factorization.

81721116 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400 (or 392 counting only the distinct ones).

The product of its digits is 672, while the sum is 27.

The square root of 81721116 is about 9039.9732300489. The cubic root of 81721116 is about 433.9550662421.

The spelling of 81721116 in words is "eighty-one million, seven hundred twenty-one thousand, one hundred sixteen".