673821 has 6 divisors (see below), whose sum is σ = 973310. Its totient is φ = 449208.

The previous prime is 673817. The next prime is 673837. The reversal of 673821 is 128376.

It can be written as a sum of positive squares in only one way, i.e., 509796 + 164025 = 714^2 + 405^2 .

It is not a de Polignac number, because 673821 - 2² = 673817 is a prime.

It is a Duffinian number.

673821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (673801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37426 + ... + 37443.

2⁶⁷³⁸²¹ is an apocalyptic number.

It is an amenable number.

673821 is a deficient number, since it is larger than the sum of its proper divisors (299489).

673821 is a wasteful number, since it uses less digits than its factorization.

673821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74875 (or 74872 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 673821 is about 820.8660061179. The cubic root of 673821 is about 87.6694295386.

The spelling of 673821 in words is "six hundred seventy-three thousand, eight hundred twenty-one".