643826 has 8 divisors (see below), whose sum is σ = 976860. Its totient is φ = 318208.

The previous prime is 643781. The next prime is 643847. The reversal of 643826 is 628346.

It can be written as a sum of positive squares in 2 ways, for example, as 483025 + 160801 = 695^2 + 401^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

643826 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 1631 + ... + 1986.

2⁶⁴³⁸²⁶ is an apocalyptic number.

643826 is a deficient number, since it is larger than the sum of its proper divisors (333034).

643826 is a wasteful number, since it uses less digits than its factorization.

643826 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3708.

The product of its digits is 6912, while the sum is 29.

The square root of 643826 is about 802.3876868447. The cubic root of 643826 is about 86.3487729311.

The spelling of 643826 in words is "six hundred forty-three thousand, eight hundred twenty-six".