221765 has 8 divisors (see below), whose sum is σ = 281880. Its totient is φ = 166912.

The previous prime is 221747. The next prime is 221773. The reversal of 221765 is 567122.

It can be written as a sum of positive squares in 4 ways, for example, as 43681 + 178084 = 209^2 + 422^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 221765 - 2⁸ = 221509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221765.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1220 + ... + 1389.

It is an arithmetic number, because the mean of its divisors is an integer number (35235).

2²²¹⁷⁶⁵ is an apocalyptic number.

It is an amenable number.

221765 is a deficient number, since it is larger than the sum of its proper divisors (60115).

221765 is a wasteful number, since it uses less digits than its factorization.

221765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2631.

The product of its digits is 840, while the sum is 23.

The square root of 221765 is about 470.9193136834. The cubic root of 221765 is about 60.5291165089.

Adding to 221765 its reverse (567122), we get a palindrome (788887).

The spelling of 221765 in words is "two hundred twenty-one thousand, seven hundred sixty-five".