15221 has 4 divisors (see below), whose sum is σ = 15744. Its totient is φ = 14700.
The previous prime is 15217. The next prime is 15227. The reversal of 15221 is 12251.
15221 is nontrivially palindromic in base 3.
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 not a de Polignac number, because 15221 - 22 = 15217 is a prime.
It is a Duffinian number.
It is a plaindrome in base 15.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (15227) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 215 + ... + 276.
It is an arithmetic number, because the mean of its divisors is an integer number (3936).
215221 is an apocalyptic number.
It is an amenable number.
15221 is a deficient number, since it is larger than the sum of its proper divisors (523).
15221 is an equidigital number, since it uses as much as digits as its factorization.
15221 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 522.
The product of its digits is 20, while the sum is 11.
The square root of 15221 is about 123.3734169098. The cubic root of 15221 is about 24.7826491540.
Adding to 15221 its reverse (12251), we get a palindrome (27472).
The spelling of 15221 in words is "fifteen thousand, two hundred twenty-one".
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