1644205397 has 2 divisors, whose sum is σ = 1644205398. Its totient is φ = 1644205396.

The previous prime is 1644205351. The next prime is 1644205403. The reversal of 1644205397 is 7935024461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1204506436 + 439698961 = 34706^2 + 20969^2 .

It is a cyclic number.

It is not a de Polignac number, because 1644205397 - 2¹⁸ = 1643943253 is a prime.

It is a super-3 number, since 3×1644205397³ (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 (1644205307) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822102698 + 822102699.

It is an arithmetic number, because the mean of its divisors is an integer number (822102699).

Almost surely, 2^1644205397 is an apocalyptic number.

It is an amenable number.

1644205397 is a deficient number, since it is larger than the sum of its proper divisors (1).

1644205397 is an equidigital number, since it uses as much as digits as its factorization.

1644205397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 181440, while the sum is 41.

The square root of 1644205397 is about 40548.8026580317. The cubic root of 1644205397 is about 1180.2808383074.

The spelling of 1644205397 in words is "one billion, six hundred forty-four million, two hundred five thousand, three hundred ninety-seven".