688138720 has 24 divisors (see below), whose sum is σ = 1625728104. Its totient is φ = 275255424.

The previous prime is 688138673. The next prime is 688138723. The reversal of 688138720 is 27831886.

It is a happy number.

It is a Smith number, since the sum of its digits (43) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688138723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2150274 + ... + 2150593.

It is an arithmetic number, because the mean of its divisors is an integer number (67738671).

Almost surely, 2^688138720 is an apocalyptic number.

It is an amenable number.

688138720 is an abundant number, since it is smaller than the sum of its proper divisors (937589384).

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

688138720 is a wasteful number, since it uses less digits than its factorization.

688138720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4300882 (or 4300874 counting only the distinct ones).

The product of its (nonzero) digits is 129024, while the sum is 43.

The square root of 688138720 is about 26232.3982891386. The cubic root of 688138720 is about 882.8603209400.

The spelling of 688138720 in words is "six hundred eighty-eight million, one hundred thirty-eight thousand, seven hundred twenty".