81923840 has 72 divisors (see below), whose sum is σ = 203091840. Its totient is φ = 31625216.

The previous prime is 81923837. The next prime is 81923843. The reversal of 81923840 is 4832918.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81923837) and next prime (81923843).

It is a self number, because there is not a number n which added to its sum of digits gives 81923840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81923843) 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, 36017 + ... + 38223.

It is an arithmetic number, because the mean of its divisors is an integer number (2820720).

Almost surely, 2^81923840 is an apocalyptic number.

81923840 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 81923840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101545920).

81923840 is an abundant number, since it is smaller than the sum of its proper divisors (121168000).

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

81923840 is a wasteful number, since it uses less digits than its factorization.

81923840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2257 (or 2243 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 81923840 is about 9051.1789287363. The cubic root of 81923840 is about 434.3136045932.

The spelling of 81923840 in words is "eighty-one million, nine hundred twenty-three thousand, eight hundred forty".