223661 has 4 divisors (see below), whose sum is σ = 225024. Its totient is φ = 222300.

The previous prime is 223637. The next prime is 223667. The reversal of 223661 is 166322.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-223661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (223667) 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, 395 + ... + 776.

It is an arithmetic number, because the mean of its divisors is an integer number (56256).

2²²³⁶⁶¹ is an apocalyptic number.

223661 is the 212-nd centered decagonal number.

It is an amenable number.

223661 is a deficient number, since it is larger than the sum of its proper divisors (1363).

223661 is a wasteful number, since it uses less digits than its factorization.

223661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1362.

The product of its digits is 432, while the sum is 20.

The square root of 223661 is about 472.9281129305. The cubic root of 223661 is about 60.7011269555.

Adding to 223661 its reverse (166322), we get a palindrome (389983).

The spelling of 223661 in words is "two hundred twenty-three thousand, six hundred sixty-one".