640901 has 2 divisors, whose sum is σ = 640902. Its totient is φ = 640900.

The previous prime is 640891. The next prime is 640907. The reversal of 640901 is 109046.

640901 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 638401 + 2500 = 799^2 + 50^2 .

It is a cyclic number.

It is not a de Polignac number, because 640901 - 2⁶ = 640837 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320450 + 320451.

It is an arithmetic number, because the mean of its divisors is an integer number (320451).

2⁶⁴⁰⁹⁰¹ is an apocalyptic number.

It is an amenable number.

640901 is a deficient number, since it is larger than the sum of its proper divisors (1).

640901 is an equidigital number, since it uses as much as digits as its factorization.

640901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 640901 is about 800.5629269458. The cubic root of 640901 is about 86.2178091730.

Adding to 640901 its reverse (109046), we get a palindrome (749947).

The spelling of 640901 in words is "six hundred forty thousand, nine hundred one".