81723840 has 224 divisors, whose sum is σ = 289681920. Its totient is φ = 19353600.

The previous prime is 81723839. The next prime is 81723857. The reversal of 81723840 is 4832718.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 749706 + ... + 749814.

Almost surely, 2^81723840 is an apocalyptic number.

81723840 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 81723840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144840960).

81723840 is an abundant number, since it is smaller than the sum of its proper divisors (207958080).

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

81723840 is a wasteful number, since it uses less digits than its factorization.

81723840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211 (or 201 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 33.

The square root of 81723840 is about 9040.1238929563. The cubic root of 81723840 is about 433.9598878457.

The spelling of 81723840 in words is "eighty-one million, seven hundred twenty-three thousand, eight hundred forty".