640870 has 16 divisors (see below), whose sum is σ = 1214640. Its totient is φ = 242784.

The previous prime is 640859. The next prime is 640873. The reversal of 640870 is 78046.

640870 = T₉₀ + T₉₁ + ... + T₁₆₅.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640873) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 1497 + ... + 1876.

It is an arithmetic number, because the mean of its divisors is an integer number (75915).

2⁶⁴⁰⁸⁷⁰ is an apocalyptic number.

640870 is a deficient number, since it is larger than the sum of its proper divisors (573770).

640870 is a wasteful number, since it uses less digits than its factorization.

640870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3399.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 640870 is about 800.5435653355. The cubic root of 640870 is about 86.2164190492.

The spelling of 640870 in words is "six hundred forty thousand, eight hundred seventy".