81739440 has 120 divisors (see below), whose sum is σ = 277334928. Its totient is φ = 21573120.

The previous prime is 81739433. The next prime is 81739453. The reversal of 81739440 is 4493718.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (120).

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

It is a junction number, because it is equal to n+sod(n) for n = 81739395 and 81739404.

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, 76510 + ... + 77570.

Almost surely, 2^81739440 is an apocalyptic number.

81739440 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 81739440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138667464).

81739440 is an abundant number, since it is smaller than the sum of its proper divisors (195595488).

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

81739440 is a wasteful number, since it uses less digits than its factorization.

81739440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1187 (or 1178 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 81739440 is about 9040.9866718185. The cubic root of 81739440 is about 433.9874984896.

The spelling of 81739440 in words is "eighty-one million, seven hundred thirty-nine thousand, four hundred forty".