81739680 has 192 divisors, whose sum is σ = 285441408. Its totient is φ = 19496960.

The previous prime is 81739663. The next prime is 81739699. The reversal of 81739680 is 8693718.

It is a Cunningham number, because it is equal to 9041²-1.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 596572 + ... + 596708.

It is an arithmetic number, because the mean of its divisors is an integer number (1486674).

Almost surely, 2^81739680 is an apocalyptic number.

81739680 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 81739680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142720704).

81739680 is an abundant number, since it is smaller than the sum of its proper divisors (203701728).

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

81739680 is a wasteful number, since it uses less digits than its factorization.

81739680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 42.

The square root of 81739680 is about 9040.9999446964. Note that the first 4 decimals coincide. The cubic root of 81739680 is about 433.9879232413.

The spelling of 81739680 in words is "eighty-one million, seven hundred thirty-nine thousand, six hundred eighty".