640929 has 16 divisors (see below), whose sum is σ = 907200. Its totient is φ = 401856.

The previous prime is 640919. The next prime is 640933. The reversal of 640929 is 929046.

640929 is digitally balanced in base 2 and base 7, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640929 - 2¹⁵ = 608161 is a prime.

640929 is strictly pandigital in base 7.

640929 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 640896 and 640905.

It is not an unprimeable number, because it can be changed into a prime (640919) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4542 + ... + 4680.

It is an arithmetic number, because the mean of its divisors is an integer number (56700).

2⁶⁴⁰⁹²⁹ is an apocalyptic number.

It is an amenable number.

640929 is a deficient number, since it is larger than the sum of its proper divisors (266271).

640929 is a wasteful number, since it uses less digits than its factorization.

640929 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224.

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 640929 is about 800.5804144494. The cubic root of 640929 is about 86.2190647302.

The spelling of 640929 in words is "six hundred forty thousand, nine hundred twenty-nine".