640745 has 8 divisors (see below), whose sum is σ = 878784. Its totient is φ = 439344.

The previous prime is 640741. The next prime is 640771. The reversal of 640745 is 547046.

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

It is a cyclic number.

It is not a de Polignac number, because 640745 - 2² = 640741 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640741) 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 7 ways as a sum of consecutive naturals, for example, 9119 + ... + 9188.

It is an arithmetic number, because the mean of its divisors is an integer number (109848).

2⁶⁴⁰⁷⁴⁵ is an apocalyptic number.

It is an amenable number.

640745 is a deficient number, since it is larger than the sum of its proper divisors (238039).

640745 is a wasteful number, since it uses less digits than its factorization.

640745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18319.

The product of its (nonzero) digits is 3360, while the sum is 26.

The square root of 640745 is about 800.4654895747. The cubic root of 640745 is about 86.2108132565.

The spelling of 640745 in words is "six hundred forty thousand, seven hundred forty-five".