51221 has 8 divisors (see below), whose sum is σ = 57024. Its totient is φ = 45760.

The previous prime is 51217. The next prime is 51229. The reversal of 51221 is 12215.

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 51221 - 2² = 51217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51229) 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, 326 + ... + 456.

It is an arithmetic number, because the mean of its divisors is an integer number (7128).

2⁵¹²²¹ is an apocalyptic number.

51221 is the 131-st octagonal number.

It is an amenable number.

51221 is a deficient number, since it is larger than the sum of its proper divisors (5803).

51221 is a wasteful number, since it uses less digits than its factorization.

51221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171.

The product of its digits is 20, while the sum is 11.

The square root of 51221 is about 226.3205691050. The cubic root of 51221 is about 37.1377867128.

Adding to 51221 its reverse (12215), we get a palindrome (63436).

It can be divided in two parts, 51 and 221, that added together give a palindrome (272).

The spelling of 51221 in words is "fifty-one thousand, two hundred twenty-one".