646445221 has 2 divisors, whose sum is σ = 646445222. Its totient is φ = 646445220.

The previous prime is 646445209. The next prime is 646445231. The reversal of 646445221 is 122544646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 436601025 + 209844196 = 20895^2 + 14486^2 .

It is a cyclic number.

It is not a de Polignac number, because 646445221 - 2²¹ = 644348069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646445231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323222610 + 323222611.

It is an arithmetic number, because the mean of its divisors is an integer number (323222611).

Almost surely, 2^646445221 is an apocalyptic number.

It is an amenable number.

646445221 is a deficient number, since it is larger than the sum of its proper divisors (1).

646445221 is an equidigital number, since it uses as much as digits as its factorization.

646445221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46080, while the sum is 34.

The square root of 646445221 is about 25425.2870386944. The cubic root of 646445221 is about 864.6570955311.

Adding to 646445221 its reverse (122544646), we get a palindrome (768989867).

The spelling of 646445221 in words is "six hundred forty-six million, four hundred forty-five thousand, two hundred twenty-one".