640786 has 8 divisors (see below), whose sum is σ = 983664. Its totient is φ = 312900.

The previous prime is 640777. The next prime is 640793. The reversal of 640786 is 687046.

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

It is a super-3 number, since 3×640786³ = 789333070361722968, which contains 333 as substring.

It is an unprimeable number.

640786 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3640 + ... + 3811.

It is an arithmetic number, because the mean of its divisors is an integer number (122958).

2⁶⁴⁰⁷⁸⁶ is an apocalyptic number.

640786 is a deficient number, since it is larger than the sum of its proper divisors (342878).

640786 is a wasteful number, since it uses less digits than its factorization.

640786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7496.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 640786 is about 800.4910992634. The cubic root of 640786 is about 86.2126520369.

The spelling of 640786 in words is "six hundred forty thousand, seven hundred eighty-six".