640726 has 8 divisors (see below), whose sum is σ = 994320. Its totient is φ = 309288.

The previous prime is 640691. The next prime is 640727. The reversal of 640726 is 627046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 640726.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640727) by changing a digit.

640726 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 5466 + ... + 5581.

It is an arithmetic number, because the mean of its divisors is an integer number (124290).

2⁶⁴⁰⁷²⁶ is an apocalyptic number.

640726 is a deficient number, since it is larger than the sum of its proper divisors (353594).

640726 is a wasteful number, since it uses less digits than its factorization.

640726 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11078.

The product of its (nonzero) digits is 2016, while the sum is 25.

The square root of 640726 is about 800.4536213923. The cubic root of 640726 is about 86.2099611122.

The spelling of 640726 in words is "six hundred forty thousand, seven hundred twenty-six".