51557221 has 2 divisors, whose sum is σ = 51557222. Its totient is φ = 51557220.

The previous prime is 51557189. The next prime is 51557239. The reversal of 51557221 is 12275515.

51557221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37344321 + 14212900 = 6111^2 + 3770^2 .

It is a cyclic number.

It is not a de Polignac number, because 51557221 - 2⁵ = 51557189 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 51557221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51557251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25778610 + 25778611.

It is an arithmetic number, because the mean of its divisors is an integer number (25778611).

Almost surely, 2^51557221 is an apocalyptic number.

It is an amenable number.

51557221 is a deficient number, since it is larger than the sum of its proper divisors (1).

51557221 is an equidigital number, since it uses as much as digits as its factorization.

51557221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3500, while the sum is 28.

The square root of 51557221 is about 7180.3357163854. The cubic root of 51557221 is about 372.1886857370.

The spelling of 51557221 in words is "fifty-one million, five hundred fifty-seven thousand, two hundred twenty-one".