1644445405 has 4 divisors (see below), whose sum is σ = 1973334492. Its totient is φ = 1315556320.

The previous prime is 1644445399. The next prime is 1644445423. The reversal of 1644445405 is 5045444461.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 467337924 + 1177107481 = 21618^2 + 34309^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1644445405 is a prime.

It is a super-2 number, since 2×1644445405² = 5408401380051228050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164444536 + ... + 164444545.

It is an arithmetic number, because the mean of its divisors is an integer number (493333623).

Almost surely, 2^1644445405 is an apocalyptic number.

It is an amenable number.

1644445405 is a deficient number, since it is larger than the sum of its proper divisors (328889087).

1644445405 is an equidigital number, since it uses as much as digits as its factorization.

1644445405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328889086.

The product of its (nonzero) digits is 153600, while the sum is 37.

The square root of 1644445405 is about 40551.7620455634. The cubic root of 1644445405 is about 1180.3382648433.

Adding to 1644445405 its reverse (5045444461), we get a palindrome (6689889866).

The spelling of 1644445405 in words is "one billion, six hundred forty-four million, four hundred forty-five thousand, four hundred five".