645560403221 has 2 divisors, whose sum is σ = 645560403222. Its totient is φ = 645560403220.

The previous prime is 645560403217. The next prime is 645560403227. The reversal of 645560403221 is 122304065546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 640728207025 + 4832196196 = 800455^2 + 69514^2 .

It is a cyclic number.

It is not a de Polignac number, because 645560403221 - 2² = 645560403217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645560403227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322780201610 + 322780201611.

It is an arithmetic number, because the mean of its divisors is an integer number (322780201611).

Almost surely, 2^645560403221 is an apocalyptic number.

It is an amenable number.

645560403221 is a deficient number, since it is larger than the sum of its proper divisors (1).

645560403221 is an equidigital number, since it uses as much as digits as its factorization.

645560403221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 172800, while the sum is 38.

Adding to 645560403221 its reverse (122304065546), we get a palindrome (767864468767).

The spelling of 645560403221 in words is "six hundred forty-five billion, five hundred sixty million, four hundred three thousand, two hundred twenty-one".