640469 has 4 divisors (see below), whose sum is σ = 654144. Its totient is φ = 626796.

The previous prime is 640463. The next prime is 640477. The reversal of 640469 is 964046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 640469 - 2¹⁶ = 574933 is a prime.

It is a super-2 number, since 2×640469² = 820401079922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640463) 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 3 ways as a sum of consecutive naturals, for example, 6767 + ... + 6860.

It is an arithmetic number, because the mean of its divisors is an integer number (163536).

2⁶⁴⁰⁴⁶⁹ is an apocalyptic number.

It is an amenable number.

640469 is a deficient number, since it is larger than the sum of its proper divisors (13675).

640469 is a wasteful number, since it uses less digits than its factorization.

640469 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13674.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 640469 is about 800.2930713183. The cubic root of 640469 is about 86.1984330836.

The spelling of 640469 in words is "six hundred forty thousand, four hundred sixty-nine".