640828 has 6 divisors (see below), whose sum is σ = 1121456. Its totient is φ = 320412.

The previous prime is 640793. The next prime is 640837. The reversal of 640828 is 828046.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 640796 and 640805.

It is a congruent number.

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 as a sum of consecutive naturals, namely, 80100 + ... + 80107.

2⁶⁴⁰⁸²⁸ is an apocalyptic number.

It is an amenable number.

640828 is a deficient number, since it is larger than the sum of its proper divisors (480628).

640828 is a wasteful number, since it uses less digits than its factorization.

640828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160211 (or 160209 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 28.

The square root of 640828 is about 800.5173327293. The cubic root of 640828 is about 86.2145355842.

It can be divided in two parts, 64082 and 8, that multiplied together give a square (512656 = 716²).

The spelling of 640828 in words is "six hundred forty thousand, eight hundred twenty-eight".