221644165681 has 3 divisors (see below), whose sum is σ = 221644636473. Its totient is φ = 221643694890.

The previous prime is 221644165669. The next prime is 221644165727. The reversal of 221644165681 is 186561446122.

The square root of 221644165681 is 470791.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 221644165681 - 2⁷ = 221644165553 is a prime.

It is a super-2 number, since 2×221644165681² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221644165601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 235396 + ... + 706186.

It is an arithmetic number, because the mean of its divisors is an integer number (73881545491).

Almost surely, 2^221644165681 is an apocalyptic number.

221644165681 is the 470791-st square number.

221644165681 is the 235396-th centered octagonal number.

It is an amenable number.

221644165681 is a deficient number, since it is larger than the sum of its proper divisors (470792).

221644165681 is an frugal number, since it uses more digits than its factorization.

221644165681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 941582 (or 470791 counting only the distinct ones).

The product of its digits is 552960, while the sum is 46.

The spelling of 221644165681 in words is "two hundred twenty-one billion, six hundred forty-four million, one hundred sixty-five thousand, six hundred eighty-one".