51505 has 4 divisors (see below), whose sum is σ = 61812. Its totient is φ = 41200.

The previous prime is 51503. The next prime is 51511. The reversal of 51505 is 50515.

51505 is nontrivially palindromic in base 9.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50515 = 5 ⋅10103.

It can be written as a sum of positive squares in 2 ways, for example, as 36864 + 14641 = 192^2 + 121^2 .

It is not a de Polignac number, because 51505 - 2¹ = 51503 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (51503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5146 + ... + 5155.

It is an arithmetic number, because the mean of its divisors is an integer number (15453).

2⁵¹⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

51505 is a deficient number, since it is larger than the sum of its proper divisors (10307).

51505 is a wasteful number, since it uses less digits than its factorization.

51505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10306.

The product of its (nonzero) digits is 125, while the sum is 16.

The square root of 51505 is about 226.9471304071. The cubic root of 51505 is about 37.2062983131.

Subtracting from 51505 its reverse (50515), we obtain a triangular number (990 = T₄₄).

The spelling of 51505 in words is "fifty-one thousand, five hundred five".