221445 has 48 divisors (see below), whose sum is σ = 474240. Its totient is φ = 93312.

The previous prime is 221413. The next prime is 221447. The reversal of 221445 is 544122.

221445 is a `hidden beast` number, since 221 + 445 = 666.

221445 is a nontrivial binomial coefficient, being equal to C(666, 2).

It is not a de Polignac number, because 221445 - 2⁵ = 221413 is a prime.

221445 is an undulating number in base 11.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 221445.

It is not an unprimeable number, because it can be changed into a prime (221447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 5967 + ... + 6003.

It is an arithmetic number, because the mean of its divisors is an integer number (9880).

2²²¹⁴⁴⁵ is an apocalyptic number.

221445 is the 665-th triangular number and also the 333-rd hexagonal number.

It is an amenable number.

221445 is an abundant number, since it is smaller than the sum of its proper divisors (252795).

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

221445 is a wasteful number, since it uses less digits than its factorization.

221445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74 (or 71 counting only the distinct ones).

The product of its digits is 320, while the sum is 18.

The square root of 221445 is about 470.5794300647. The cubic root of 221445 is about 60.4999886164.

Adding to 221445 its reverse (544122), we get a palindrome (765567).

It can be divided in two parts, 221 and 445, that added together give a palindrome (666).

The spelling of 221445 in words is "two hundred twenty-one thousand, four hundred forty-five".