681920640 has 512 divisors, whose sum is σ = 2663424000. Its totient is φ = 164229120.

The previous prime is 681920639. The next prime is 681920669. The reversal of 681920640 is 46029186.

681920640 is a `hidden beast` number, since 6 + 8 + 1 + 9 + 2 + 0 + 640 = 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 = 681920595 and 681920604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 10177887 + ... + 10177953.

It is an arithmetic number, because the mean of its divisors is an integer number (5202000).

Almost surely, 2^681920640 is an apocalyptic number.

681920640 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 681920640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1331712000).

681920640 is an abundant number, since it is smaller than the sum of its proper divisors (1981503360).

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

681920640 is a wasteful number, since it uses less digits than its factorization.

681920640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145 (or 127 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 681920640 is about 26113.6102444683. The cubic root of 681920640 is about 880.1930705852.

The spelling of 681920640 in words is "six hundred eighty-one million, nine hundred twenty thousand, six hundred forty".