640826 has 8 divisors (see below), whose sum is σ = 1003104. Its totient is φ = 306460.

The previous prime is 640793. The next prime is 640837. The reversal of 640826 is 628046.

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

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 640795 and 640804.

It is an unprimeable 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, 6920 + ... + 7011.

It is an arithmetic number, because the mean of its divisors is an integer number (125388).

2⁶⁴⁰⁸²⁶ is an apocalyptic number.

640826 is a deficient number, since it is larger than the sum of its proper divisors (362278).

640826 is a wasteful number, since it uses less digits than its factorization.

640826 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13956.

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 640826 is about 800.5160835361. The cubic root of 640826 is about 86.2144458933.

The spelling of 640826 in words is "six hundred forty thousand, eight hundred twenty-six".