1644475668 has 72 divisors (see below), whose sum is σ = 4307565696. Its totient is φ = 487703040.

The previous prime is 1644475667. The next prime is 1644475687. The reversal of 1644475668 is 8665744461.

It is a self number, because there is not a number n which added to its sum of digits gives 1644475668.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644475661) 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 23 ways as a sum of consecutive naturals, for example, 56196 + ... + 80292.

Almost surely, 2^1644475668 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1644475668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2153782848).

1644475668 is an abundant number, since it is smaller than the sum of its proper divisors (2663090028).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1644475668 is a wasteful number, since it uses less digits than its factorization.

1644475668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24173 (or 24160 counting only the distinct ones).

The product of its digits is 3870720, while the sum is 51.

The square root of 1644475668 is about 40552.1351842292. The cubic root of 1644475668 is about 1180.3455054522.

The spelling of 1644475668 in words is "one billion, six hundred forty-four million, four hundred seventy-five thousand, six hundred sixty-eight".