1644261313 has 4 divisors (see below), whose sum is σ = 1644346288. Its totient is φ = 1644176340.

The previous prime is 1644261263. The next prime is 1644261319. The reversal of 1644261313 is 3131624461.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 3131624461 = 7 ⋅447374923.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1644261313 is a prime.

It is a super-3 number, since 3×1644261313³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1644261319) 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 in 3 ways as a sum of consecutive naturals, for example, 2218 + ... + 57388.

It is an arithmetic number, because the mean of its divisors is an integer number (411086572).

Almost surely, 2^1644261313 is an apocalyptic number.

It is an amenable number.

1644261313 is a deficient number, since it is larger than the sum of its proper divisors (84975).

1644261313 is an equidigital number, since it uses as much as digits as its factorization.

1644261313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84974.

The product of its digits is 10368, while the sum is 31.

The square root of 1644261313 is about 40549.4921423191. The cubic root of 1644261313 is about 1180.2942177865.

Adding to 1644261313 its reverse (3131624461), we get a palindrome (4775885774).

The spelling of 1644261313 in words is "one billion, six hundred forty-four million, two hundred sixty-one thousand, three hundred thirteen".