81735840 has 144 divisors (see below), whose sum is σ = 288078336. Its totient is φ = 21081600.

The previous prime is 81735817. The next prime is 81735877. The reversal of 81735840 is 4853718.

81735840 is a `hidden beast` number, since 8 + 1 + 73 + 584 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

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 = 81735795 and 81735804.

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, 43725 + ... + 45555.

It is an arithmetic number, because the mean of its divisors is an integer number (2000544).

Almost surely, 2^81735840 is an apocalyptic number.

81735840 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 81735840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144039168).

81735840 is an abundant number, since it is smaller than the sum of its proper divisors (206342496).

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

81735840 is a wasteful number, since it uses less digits than its factorization.

81735840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1883 (or 1872 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 81735840 is about 9040.7875763121. The cubic root of 81735840 is about 433.9811271144.

The spelling of 81735840 in words is "eighty-one million, seven hundred thirty-five thousand, eight hundred forty".