81681336 has 96 divisors (see below), whose sum is σ = 243285120. Its totient is φ = 24552000.

The previous prime is 81681329. The next prime is 81681343. The reversal of 81681336 is 63318618.

It is an interprime number because it is at equal distance from previous prime (81681329) and next prime (81681343).

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

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 81681336.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 119251 + ... + 119933.

It is an arithmetic number, because the mean of its divisors is an integer number (2534220).

Almost surely, 2^81681336 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 81681336, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (121642560).

81681336 is an abundant number, since it is smaller than the sum of its proper divisors (161603784).

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

81681336 is a wasteful number, since it uses less digits than its factorization.

81681336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857 (or 850 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 81681336 is about 9037.7727344739. The cubic root of 81681336 is about 433.8846416274.

The spelling of 81681336 in words is "eighty-one million, six hundred eighty-one thousand, three hundred thirty-six".