640626 has 24 divisors (see below), whose sum is σ = 1491120. Its totient is φ = 182952.

The previous prime is 640621. The next prime is 640631. The reversal of 640626 is 626046.

640626 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (640621) and next prime (640631).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 640596 and 640605.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640626.

It is not an unprimeable number, because it can be changed into a prime (640621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 796 + ... + 1383.

It is an arithmetic number, because the mean of its divisors is an integer number (62130).

2⁶⁴⁰⁶²⁶ is an apocalyptic number.

640626 is an abundant number, since it is smaller than the sum of its proper divisors (850494).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640626 is a wasteful number, since it uses less digits than its factorization.

640626 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2198 (or 2191 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 640626 is about 800.3911543739. The cubic root of 640626 is about 86.2054758644.

The spelling of 640626 in words is "six hundred forty thousand, six hundred twenty-six".