640556801 has 2 divisors, whose sum is σ = 640556802. Its totient is φ = 640556800.

The previous prime is 640556797. The next prime is 640556803. The reversal of 640556801 is 108655046.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 627452401 + 13104400 = 25049^2 + 3620^2 .

It is a cyclic number.

It is not a de Polignac number, because 640556801 - 2² = 640556797 is a prime.

Together with 640556803, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640556803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320278400 + 320278401.

It is an arithmetic number, because the mean of its divisors is an integer number (320278401).

Almost surely, 2^640556801 is an apocalyptic number.

It is an amenable number.

640556801 is a deficient number, since it is larger than the sum of its proper divisors (1).

640556801 is an equidigital number, since it uses as much as digits as its factorization.

640556801 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 28800, while the sum is 35.

The square root of 640556801 is about 25309.2236348727. The cubic root of 640556801 is about 862.0237184452.

The spelling of 640556801 in words is "six hundred forty million, five hundred fifty-six thousand, eight hundred one".