644209199 has 4 divisors (see below), whose sum is σ = 653282640. Its totient is φ = 635135760.

The previous prime is 644209157. The next prime is 644209211. The reversal of 644209199 is 991902446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 991902446 = 2 ⋅495951223.

It is a cyclic number.

It is not a de Polignac number, because 644209199 - 2¹² = 644205103 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644209129) 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 in 3 ways as a sum of consecutive naturals, for example, 4536614 + ... + 4536755.

It is an arithmetic number, because the mean of its divisors is an integer number (163320660).

Almost surely, 2^644209199 is an apocalyptic number.

644209199 is a deficient number, since it is larger than the sum of its proper divisors (9073441).

644209199 is an equidigital number, since it uses as much as digits as its factorization.

644209199 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9073440.

The product of its (nonzero) digits is 139968, while the sum is 44.

The square root of 644209199 is about 25381.2765439408. The cubic root of 644209199 is about 863.6590085119.

The spelling of 644209199 in words is "six hundred forty-four million, two hundred nine thousand, one hundred ninety-nine".