646123321 has 2 divisors, whose sum is σ = 646123322. Its totient is φ = 646123320.

The previous prime is 646123319. The next prime is 646123327. The reversal of 646123321 is 123321646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 362369296 + 283754025 = 19036^2 + 16845^2 .

It is a cyclic number.

It is not a de Polignac number, because 646123321 - 2¹ = 646123319 is a prime.

Together with 646123319, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 646123321.

It is not a weakly prime, because it can be changed into another prime (646123327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323061660 + 323061661.

It is an arithmetic number, because the mean of its divisors is an integer number (323061661).

Almost surely, 2^646123321 is an apocalyptic number.

It is an amenable number.

646123321 is a deficient number, since it is larger than the sum of its proper divisors (1).

646123321 is an equidigital number, since it uses as much as digits as its factorization.

646123321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 28.

The square root of 646123321 is about 25418.9559384330. The cubic root of 646123321 is about 864.5135518753.

Adding to 646123321 its reverse (123321646), we get a palindrome (769444967).

The spelling of 646123321 in words is "six hundred forty-six million, one hundred twenty-three thousand, three hundred twenty-one".