221506 has 4 divisors (see below), whose sum is σ = 332262. Its totient is φ = 110752.

The previous prime is 221497. The next prime is 221509. The reversal of 221506 is 605122.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 126025 + 95481 = 355^2 + 309^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 221506.

It is not an unprimeable number, because it can be changed into a prime (221509) by changing a digit.

221506 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 55375 + ... + 55378.

2²²¹⁵⁰⁶ is an apocalyptic number.

221506 is a deficient number, since it is larger than the sum of its proper divisors (110756).

221506 is a wasteful number, since it uses less digits than its factorization.

221506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110755.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 221506 is about 470.6442393146. The cubic root of 221506 is about 60.5055432846.

Adding to 221506 its reverse (605122), we get a palindrome (826628).

It can be divided in two parts, 221 and 506, that added together give a palindrome (727).

The spelling of 221506 in words is "two hundred twenty-one thousand, five hundred six".