54991 has 4 divisors (see below), whose sum is σ = 55552.
Its totient is φ = 54432.
The previous prime is 54983. The next prime is 55001. The reversal of 54991 is 19945.
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: 19945 = 5 ⋅3989.
It is a cyclic number.
It is not a de Polignac number, because 54991 - 23 = 54983 is a prime.
It is the 235-th Hogben number.
It is a Duffinian number.
54991 is a lucky number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (54941) by changing a digit.
It is a nontrivial repunit in base 234.
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 3 ways as a sum of consecutive naturals, for example, 90 + ... + 343.
It is an arithmetic number, because the mean of its divisors is an integer number (13888).
254991 is an apocalyptic number.
54991 is a deficient number, since it is larger than the sum of its proper divisors (561).
54991 is a wasteful number, since it uses less digits than its factorization.
54991 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 560.
The product of its digits is 1620, while the sum is 28.
The square root of 54991 is about 234.5015991417.
The cubic root of 54991 is about 38.0274501568.
The spelling of 54991 in words is "fifty-four thousand, nine hundred ninety-one".