684778 has 4 divisors (see below), whose sum is σ = 1027170. Its totient is φ = 342388.

The previous prime is 684773. The next prime is 684791. The reversal of 684778 is 877486.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 400689 + 284089 = 633^2 + 533^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 684778.

It is not an unprimeable number, because it can be changed into a prime (684773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 171193 + ... + 171196.

2⁶⁸⁴⁷⁷⁸ is an apocalyptic number.

684778 is a deficient number, since it is larger than the sum of its proper divisors (342392).

684778 is a wasteful number, since it uses less digits than its factorization.

684778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 342391.

The product of its digits is 75264, while the sum is 40.

The square root of 684778 is about 827.5131418896. The cubic root of 684778 is about 88.1420742196.

The spelling of 684778 in words is "six hundred eighty-four thousand, seven hundred seventy-eight".