51865 has 16 divisors (see below), whose sum is σ = 72576. Its totient is φ = 35200.

The previous prime is 51859. The next prime is 51869. The reversal of 51865 is 56815.

51865 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a de Polignac number, because none of the positive numbers 2^k-51865 is a prime.

It is a Duffinian number.

Its product of digits (1200) is a multiple of the sum of its prime divisors (80).

51865 is a lucky number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (51869) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1245 + ... + 1285.

It is an arithmetic number, because the mean of its divisors is an integer number (4536).

2⁵¹⁸⁶⁵ is an apocalyptic number.

51865 is a gapful number since it is divisible by the number (55) formed by its first and last digit.

It is an amenable number.

51865 is a deficient number, since it is larger than the sum of its proper divisors (20711).

51865 is a wasteful number, since it uses less digits than its factorization.

51865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80.

The product of its digits is 1200, while the sum is 25.

The square root of 51865 is about 227.7388855685. The cubic root of 51865 is about 37.2927829980.

Subtracting 51865 from its reverse (56815), we obtain a triangular number (4950 = T₉₉).

It can be divided in two parts, 518 and 65, that multiplied together give a triangular number (33670 = T₂₅₉).

The spelling of 51865 in words is "fifty-one thousand, eight hundred sixty-five".