51518221 has 6 divisors (see below), whose sum is σ = 52419822. Its totient is φ = 50618520.

The previous prime is 51518219. The next prime is 51518261. The reversal of 51518221 is 12281515.

It can be written as a sum of positive squares in only one way, i.e., 30404196 + 21114025 = 5514^2 + 4595^2 .

It is not a de Polignac number, because 51518221 - 2¹ = 51518219 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 (51518261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55600 + ... + 56518.

It is an arithmetic number, because the mean of its divisors is an integer number (8736637).

Almost surely, 2^51518221 is an apocalyptic number.

It is an amenable number.

51518221 is a deficient number, since it is larger than the sum of its proper divisors (901601).

51518221 is an frugal number, since it uses more digits than its factorization.

51518221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1899 (or 980 counting only the distinct ones).

The product of its digits is 800, while the sum is 25.

The square root of 51518221 is about 7177.6194521582. The cubic root of 51518221 is about 372.0948157934.

Adding to 51518221 its reverse (12281515), we get a palindrome (63799736).

The spelling of 51518221 in words is "fifty-one million, five hundred eighteen thousand, two hundred twenty-one".