221509 has 2 divisors, whose sum is σ = 221510. Its totient is φ = 221508.

The previous prime is 221497. The next prime is 221537. The reversal of 221509 is 905122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 172225 + 49284 = 415^2 + 222^2 .

It is a cyclic number.

It is not a de Polignac number, because 221509 - 2⁵ = 221477 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110754 + 110755.

It is an arithmetic number, because the mean of its divisors is an integer number (110755).

2²²¹⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

221509 is a deficient number, since it is larger than the sum of its proper divisors (1).

221509 is an equidigital number, since it uses as much as digits as its factorization.

221509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 221509 is about 470.6474264245. The cubic root of 221509 is about 60.5058164387.

The spelling of 221509 in words is "two hundred twenty-one thousand, five hundred nine".