688690 has 16 divisors (see below), whose sum is σ = 1261080. Its totient is φ = 270720.

The previous prime is 688679. The next prime is 688697. The reversal of 688690 is 96886.

It can be written as a sum of positive squares in 4 ways, for example, as 194481 + 494209 = 441^2 + 703^2 .

It is a super-2 number, since 2×688690² = 948587832200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (688697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 46 + ... + 1174.

2⁶⁸⁸⁶⁹⁰ is an apocalyptic number.

688690 is a deficient number, since it is larger than the sum of its proper divisors (572390).

688690 is a wasteful number, since it uses less digits than its factorization.

688690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1197.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 688690 is about 829.8734843336. The cubic root of 688690 is about 88.3096016308.

It can be divided in two parts, 688 and 690, that added together give a triangular number (1378 = T₅₂).

The spelling of 688690 in words is "six hundred eighty-eight thousand, six hundred ninety".