181221 has 8 divisors (see below), whose sum is σ = 250080. Its totient is φ = 116592.

The previous prime is 181219. The next prime is 181243. The reversal of 181221 is 122181.

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

It is not a de Polignac number, because 181221 - 2¹ = 181219 is a prime.

It is a Curzon number.

181221 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 181221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 955 + ... + 1128.

It is an arithmetic number, because the mean of its divisors is an integer number (31260).

2¹⁸¹²²¹ is an apocalyptic number.

It is an amenable number.

181221 is a deficient number, since it is larger than the sum of its proper divisors (68859).

181221 is a wasteful number, since it uses less digits than its factorization.

181221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2115.

The product of its digits is 32, while the sum is 15.

The square root of 181221 is about 425.7005990130. The cubic root of 181221 is about 56.5895413673.

The spelling of 181221 in words is "one hundred eighty-one thousand, two hundred twenty-one".