640761 has 8 divisors (see below), whose sum is σ = 932064. Its totient is φ = 388320.

The previous prime is 640741. The next prime is 640771. The reversal of 640761 is 167046.

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

It is not a de Polignac number, because 640761 - 2⁹ = 640249 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640741) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9676 + ... + 9741.

It is an arithmetic number, because the mean of its divisors is an integer number (116508).

2⁶⁴⁰⁷⁶¹ is an apocalyptic number.

It is an amenable number.

640761 is a deficient number, since it is larger than the sum of its proper divisors (291303).

640761 is a wasteful number, since it uses less digits than its factorization.

640761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19431.

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 640761 is about 800.4754836970. The cubic root of 640761 is about 86.2115308387.

The spelling of 640761 in words is "six hundred forty thousand, seven hundred sixty-one".