688682721 has 32 divisors (see below), whose sum is σ = 1011502080. Its totient is φ = 414849600.

The previous prime is 688682717. The next prime is 688682723. The reversal of 688682721 is 127286886.

It is not a de Polignac number, because 688682721 - 2² = 688682717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (688682723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 708766 + ... + 709736.

It is an arithmetic number, because the mean of its divisors is an integer number (31609440).

Almost surely, 2^688682721 is an apocalyptic number.

It is an amenable number.

688682721 is a deficient number, since it is larger than the sum of its proper divisors (322819359).

688682721 is a wasteful number, since it uses less digits than its factorization.

688682721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1557.

The product of its digits is 516096, while the sum is 48.

The square root of 688682721 is about 26242.7651172661. The cubic root of 688682721 is about 883.0929050492.

The spelling of 688682721 in words is "six hundred eighty-eight million, six hundred eighty-two thousand, seven hundred twenty-one".