684661 has 4 divisors (see below), whose sum is σ = 708300. Its totient is φ = 661024.

The previous prime is 684647. The next prime is 684683. The reversal of 684661 is 166486.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166486 = 2 ⋅83243.

It can be written as a sum of positive squares in 2 ways, for example, as 220900 + 463761 = 470^2 + 681^2 .

It is a cyclic number.

It is not a de Polignac number, because 684661 - 2¹³ = 676469 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684961) 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 in 3 ways as a sum of consecutive naturals, for example, 11776 + ... + 11833.

It is an arithmetic number, because the mean of its divisors is an integer number (177075).

2⁶⁸⁴⁶⁶¹ is an apocalyptic number.

It is an amenable number.

684661 is a deficient number, since it is larger than the sum of its proper divisors (23639).

684661 is a wasteful number, since it uses less digits than its factorization.

684661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23638.

The product of its digits is 6912, while the sum is 31.

The square root of 684661 is about 827.4424451284. The cubic root of 684661 is about 88.1370539989.

The spelling of 684661 in words is "six hundred eighty-four thousand, six hundred sixty-one".