51211221 has 4 divisors (see below), whose sum is σ = 68281632. Its totient is φ = 34140812.

The previous prime is 51211217. The next prime is 51211231. The reversal of 51211221 is 12211215.

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 51211221 - 2² = 51211217 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 51211221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51211211) 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, 8535201 + ... + 8535206.

It is an arithmetic number, because the mean of its divisors is an integer number (17070408).

Almost surely, 2^51211221 is an apocalyptic number.

It is an amenable number.

51211221 is a deficient number, since it is larger than the sum of its proper divisors (17070411).

51211221 is a wasteful number, since it uses less digits than its factorization.

51211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17070410.

The product of its digits is 40, while the sum is 15.

The square root of 51211221 is about 7156.2015762554. The cubic root of 51211221 is about 371.3542314098.

Adding to 51211221 its reverse (12211215), we get a palindrome (63422436).

The spelling of 51211221 in words is "fifty-one million, two hundred eleven thousand, two hundred twenty-one".