1644218663 has 4 divisors (see below), whose sum is σ = 1662693120. Its totient is φ = 1625744208.

The previous prime is 1644218651. The next prime is 1644218671. The reversal of 1644218663 is 3668124461.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3668124461 = 181 ⋅20265881.

It is a cyclic number.

It is not a de Polignac number, because 1644218663 - 2¹⁰ = 1644217639 is a prime.

It is a super-3 number, since 3×1644218663³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1644218663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644218263) 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 in 3 ways as a sum of consecutive naturals, for example, 9237095 + ... + 9237272.

It is an arithmetic number, because the mean of its divisors is an integer number (415673280).

Almost surely, 2^1644218663 is an apocalyptic number.

1644218663 is a deficient number, since it is larger than the sum of its proper divisors (18474457).

1644218663 is an equidigital number, since it uses as much as digits as its factorization.

1644218663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18474456.

The product of its digits is 165888, while the sum is 41.

The square root of 1644218663 is about 40548.9662383642. The cubic root of 1644218663 is about 1180.2840125992.

The spelling of 1644218663 in words is "one billion, six hundred forty-four million, two hundred eighteen thousand, six hundred sixty-three".