640629 has 20 divisors (see below), whose sum is σ = 1045440. Its totient is φ = 387720.

The previous prime is 640621. The next prime is 640631. The reversal of 640629 is 926046.

It is not a de Polignac number, because 640629 - 2³ = 640621 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640621) 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 19 ways as a sum of consecutive naturals, for example, 532 + ... + 1250.

It is an arithmetic number, because the mean of its divisors is an integer number (52272).

2⁶⁴⁰⁶²⁹ is an apocalyptic number.

It is an amenable number.

640629 is a deficient number, since it is larger than the sum of its proper divisors (404811).

640629 is a wasteful number, since it uses less digits than its factorization.

640629 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 742 (or 733 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 640629 is about 800.3930284554. The cubic root of 640629 is about 86.2056104286.

The spelling of 640629 in words is "six hundred forty thousand, six hundred twenty-nine".