1644445221 has 8 divisors (see below), whose sum is σ = 2193143424. Its totient is φ = 1096021920.

The previous prime is 1644445141. The next prime is 1644445247. The reversal of 1644445221 is 1225444461.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1644445221 - 2¹³ = 1644437029 is a prime.

It is a super-3 number, since 3×1644445221³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644245221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 54336 + ... + 79001.

It is an arithmetic number, because the mean of its divisors is an integer number (274142928).

Almost surely, 2^1644445221 is an apocalyptic number.

It is an amenable number.

1644445221 is a deficient number, since it is larger than the sum of its proper divisors (548698203).

1644445221 is a wasteful number, since it uses less digits than its factorization.

1644445221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137451.

The product of its digits is 30720, while the sum is 33.

The square root of 1644445221 is about 40551.7597768580. The cubic root of 1644445221 is about 1180.3382208199.

Adding to 1644445221 its reverse (1225444461), we get a palindrome (2869889682).

The spelling of 1644445221 in words is "one billion, six hundred forty-four million, four hundred forty-five thousand, two hundred twenty-one".