1644312391 has 2 divisors, whose sum is σ = 1644312392. Its totient is φ = 1644312390.

The previous prime is 1644312379. The next prime is 1644312427. The reversal of 1644312391 is 1932134461.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1644312391 is a prime.

It is a super-3 number, since 3×1644312391³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1644312361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822156195 + 822156196.

It is an arithmetic number, because the mean of its divisors is an integer number (822156196).

Almost surely, 2^1644312391 is an apocalyptic number.

1644312391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1644312391 is an equidigital number, since it uses as much as digits as its factorization.

1644312391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 34.

The square root of 1644312391 is about 40550.1219603591. The cubic root of 1644312391 is about 1180.3064393726.

The spelling of 1644312391 in words is "one billion, six hundred forty-four million, three hundred twelve thousand, three hundred ninety-one".