81657744 has 80 divisors (see below), whose sum is σ = 253793280. Its totient is φ = 22101120.

The previous prime is 81657733. The next prime is 81657787. The reversal of 81657744 is 44775618.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 81657696 and 81657705.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12 + ... + 12779.

It is an arithmetic number, because the mean of its divisors is an integer number (3172416).

Almost surely, 2^81657744 is an apocalyptic number.

81657744 is a gapful number since it is divisible by the number (84) 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 81657744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126896640).

81657744 is an abundant number, since it is smaller than the sum of its proper divisors (172135536).

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

81657744 is a wasteful number, since it uses less digits than its factorization.

81657744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12828 (or 12822 counting only the distinct ones).

The product of its digits is 188160, while the sum is 42.

The square root of 81657744 is about 9036.4674513883. The cubic root of 81657744 is about 433.8428646739.

The spelling of 81657744 in words is "eighty-one million, six hundred fifty-seven thousand, seven hundred forty-four".