81399040 has 72 divisors (see below), whose sum is σ = 205299360. Its totient is φ = 30836736.

The previous prime is 81399011. The next prime is 81399041. The reversal of 81399040 is 4099318.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 81398987 and 81399005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81399041) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22647 + ... + 25993.

It is an arithmetic number, because the mean of its divisors is an integer number (2851380).

Almost surely, 2^81399040 is an apocalyptic number.

81399040 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 81399040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102649680).

81399040 is an abundant number, since it is smaller than the sum of its proper divisors (123900320).

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

81399040 is a wasteful number, since it uses less digits than its factorization.

81399040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3387 (or 3373 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 81399040 is about 9022.1416526233. The cubic root of 81399040 is about 433.3842201911.

The spelling of 81399040 in words is "eighty-one million, three hundred ninety-nine thousand, forty".