551 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 155 = 5 ⋅31.
It is a cyclic number.
It is a Duffinian number.
It is a plaindrome in base 12, base 13, base 15 and base 16.
It is a nialpdrome in base 10.
It is a congruent number.
551 is the 11-th centered decagonal number.
551 is a wasteful number, since it uses less digits than its factorization.
551 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 48.
The square root of 551 is about 23.4733891886. The cubic root of 551 is about 8.1981752831.
Adding to 551 its product of digits (25), we get a square (576 = 242).
The spelling of 551 in words is "five hundred fifty-one", and thus it is an aban number.