681531840 has 448 divisors, whose sum is σ = 2686141440. Its totient is φ = 161280000.

The previous prime is 681531793. The next prime is 681531847. The reversal of 681531840 is 48135186.

681531840 is a `hidden beast` number, since 6 + 81 + 531 + 8 + 40 = 666.

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 = 681531795 and 681531804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681531847) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 6747790 + ... + 6747890.

Almost surely, 2^681531840 is an apocalyptic number.

681531840 is a gapful number since it is divisible by the number (60) 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 681531840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1343070720).

681531840 is an abundant number, since it is smaller than the sum of its proper divisors (2004609600).

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

681531840 is a wasteful number, since it uses less digits than its factorization.

681531840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209 (or 193 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 681531840 is about 26106.1647891834. The cubic root of 681531840 is about 880.0257568219.

The spelling of 681531840 in words is "six hundred eighty-one million, five hundred thirty-one thousand, eight hundred forty".