646738109 has 2 divisors, whose sum is σ = 646738110. Its totient is φ = 646738108.

The previous prime is 646738087. The next prime is 646738111. The reversal of 646738109 is 901837646.

646738109 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 478646884 + 168091225 = 21878^2 + 12965^2 .

It is a cyclic number.

It is not a de Polignac number, because 646738109 - 2²⁸ = 378302653 is a prime.

Together with 646738111, 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 646738109.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646738129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323369054 + 323369055.

It is an arithmetic number, because the mean of its divisors is an integer number (323369055).

Almost surely, 2^646738109 is an apocalyptic number.

It is an amenable number.

646738109 is a deficient number, since it is larger than the sum of its proper divisors (1).

646738109 is an equidigital number, since it uses as much as digits as its factorization.

646738109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 217728, while the sum is 44.

The square root of 646738109 is about 25431.0461640885. The cubic root of 646738109 is about 864.7876605772.

The spelling of 646738109 in words is "six hundred forty-six million, seven hundred thirty-eight thousand, one hundred nine".