684979 has 4 divisors (see below), whose sum is σ = 687960. Its totient is φ = 682000.

The previous prime is 684977. The next prime is 684989. The reversal of 684979 is 979486.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 979486 = 2 ⋅489743.

It is a cyclic number.

It is not a de Polignac number, because 684979 - 2¹ = 684977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (684973) 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, 1114 + ... + 1615.

It is an arithmetic number, because the mean of its divisors is an integer number (171990).

2⁶⁸⁴⁹⁷⁹ is an apocalyptic number.

684979 is a deficient number, since it is larger than the sum of its proper divisors (2981).

684979 is a wasteful number, since it uses less digits than its factorization.

684979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2980.

The product of its digits is 108864, while the sum is 43.

The square root of 684979 is about 827.6345812011. The cubic root of 684979 is about 88.1506973665.

The spelling of 684979 in words is "six hundred eighty-four thousand, nine hundred seventy-nine".