640823836 has 6 divisors (see below), whose sum is σ = 1121441720. Its totient is φ = 320411916.

The previous prime is 640823801. The next prime is 640823837. The reversal of 640823836 is 638328046.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640823837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80102976 + ... + 80102983.

Almost surely, 2^640823836 is an apocalyptic number.

It is an amenable number.

640823836 is a deficient number, since it is larger than the sum of its proper divisors (480617884).

640823836 is a wasteful number, since it uses less digits than its factorization.

640823836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160205963 (or 160205961 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 40.

The square root of 640823836 is about 25314.4985334492. The cubic root of 640823836 is about 862.1434884762.

The spelling of 640823836 in words is "six hundred forty million, eight hundred twenty-three thousand, eight hundred thirty-six".