640001 has 6 divisors (see below), whose sum is σ = 663702.
Its totient is φ = 617120.
The previous prime is 639997. The next prime is 640007. The reversal of 640001 is 100046.
Adding to 640001 its reverse (100046), we get a palindrome (740047).
It is a Cunningham number, because it is equal to 8002+1.
It can be written as a sum of positive squares in 3 ways, for example, as 1600 + 638401 = 40^2 + 799^2
It is not a de Polignac number, because 640001 - 22 = 639997 is a prime.
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (640007) by changing a digit.
It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 461 + ... + 1221.
It is an arithmetic number, because the mean of its divisors is an integer number (110617).
It is a Proth number, since it is equal to 625 ⋅ 210 + 1 and 625 < 210.
2640001 is an apocalyptic number.
It is an amenable number.
640001 is a deficient number, since it is larger than the sum of its proper divisors (23701).
640001 is an equidigital number, since it uses as much as digits as its factorization.
640001 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 819 (or 790 counting only the distinct ones).
The product of its (nonzero) digits is 24, while the sum is 11.
The square root of 640001 is about 800.0006249998.
Note that the first 3 decimals coincide.
The cubic root of 640001 is about 86.1774324853.
The spelling of 640001 in words is "six hundred forty thousand, one".