81943840 has 48 divisors (see below), whose sum is σ = 211196160. Its totient is φ = 29797120.

The previous prime is 81943837. The next prime is 81943843. The reversal of 81943840 is 4834918.

It is an interprime number because it is at equal distance from previous prime (81943837) and next prime (81943843).

It is a self number, because there is not a number n which added to its sum of digits gives 81943840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81943843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21520 + ... + 25039.

It is an arithmetic number, because the mean of its divisors is an integer number (4399920).

Almost surely, 2^81943840 is an apocalyptic number.

81943840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81943840 is an abundant number, since it is smaller than the sum of its proper divisors (129252320).

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

81943840 is a wasteful number, since it uses less digits than its factorization.

81943840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46585 (or 46577 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 81943840 is about 9052.2836897658. The cubic root of 81943840 is about 434.3489445924.

The spelling of 81943840 in words is "eighty-one million, nine hundred forty-three thousand, eight hundred forty".