221009 has 4 divisors (see below), whose sum is σ = 228660. Its totient is φ = 213360.

The previous prime is 220973. The next prime is 221021. The reversal of 221009 is 900122.

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

It can be written as a sum of positive squares in 2 ways, for example, as 160000 + 61009 = 400^2 + 247^2 .

It is a cyclic number.

It is not a de Polignac number, because 221009 - 2¹⁶ = 155473 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 220984 and 221002.

It is not an unprimeable number, because it can be changed into a prime (221059) 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 3 ways as a sum of consecutive naturals, for example, 3782 + ... + 3839.

It is an arithmetic number, because the mean of its divisors is an integer number (57165).

2²²¹⁰⁰⁹ is an apocalyptic number.

221009 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

221009 is a deficient number, since it is larger than the sum of its proper divisors (7651).

221009 is an equidigital number, since it uses as much as digits as its factorization.

221009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7650.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 221009 is about 470.1159431459. The cubic root of 221009 is about 60.4602566653.

The spelling of 221009 in words is "two hundred twenty-one thousand, nine".