688712640 has 420 divisors, whose sum is σ = 2798018280. Its totient is φ = 143109120.

The previous prime is 688712623. The next prime is 688712657. The reversal of 688712640 is 46217886.

It is an interprime number because it is at equal distance from previous prime (688712623) and next prime (688712657).

It is a tau number, because it is divible by the number of its divisors (420).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its 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 = 688712592 and 688712601.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 62610235 + ... + 62610245.

Almost surely, 2^688712640 is an apocalyptic number.

688712640 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 688712640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1399009140).

688712640 is an abundant number, since it is smaller than the sum of its proper divisors (2109305640).

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

688712640 is an equidigital number, since it uses as much as digits as its factorization.

688712640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78 (or 28 counting only the distinct ones).

The product of its (nonzero) digits is 129024, while the sum is 42.

The square root of 688712640 is about 26243.3351539015. The cubic root of 688712640 is about 883.1056931703.

The spelling of 688712640 in words is "six hundred eighty-eight million, seven hundred twelve thousand, six hundred forty".