81648640 has 88 divisors (see below), whose sum is σ = 201621312. Its totient is φ = 31703040.

The previous prime is 81648607. The next prime is 81648647. The reversal of 81648640 is 4684618.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a self number, because there is not a number n which added to its sum of digits gives 81648640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81648647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 189225 + ... + 189655.

Almost surely, 2^81648640 is an apocalyptic number.

81648640 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 81648640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100810656).

81648640 is an abundant number, since it is smaller than the sum of its proper divisors (119972672).

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

81648640 is a wasteful number, since it uses less digits than its factorization.

81648640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 493 (or 475 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 37.

The square root of 81648640 is about 9035.9637006796. The cubic root of 81648640 is about 433.8267410664.

The spelling of 81648640 in words is "eighty-one million, six hundred forty-eight thousand, six hundred forty".