640169 has 4 divisors (see below), whose sum is σ = 677844. Its totient is φ = 602496.

The previous prime is 640163. The next prime is 640193. The reversal of 640169 is 961046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 506944 + 133225 = 712^2 + 365^2 .

It is a cyclic number.

It is not a de Polignac number, because 640169 - 2⁴ = 640153 is a prime.

It is a super-2 number, since 2×640169² = 819632697122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640163) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18812 + ... + 18845.

It is an arithmetic number, because the mean of its divisors is an integer number (169461).

2⁶⁴⁰¹⁶⁹ is an apocalyptic number.

It is an amenable number.

640169 is a deficient number, since it is larger than the sum of its proper divisors (37675).

640169 is a wasteful number, since it uses less digits than its factorization.

640169 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37674.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 640169 is about 800.1056180280. The cubic root of 640169 is about 86.1849723392.

The spelling of 640169 in words is "six hundred forty thousand, one hundred sixty-nine".