51861 has 8 divisors (see below), whose sum is σ = 70560. Its totient is φ = 33872.

The previous prime is 51859. The next prime is 51869. The reversal of 51861 is 16815.

51861 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51861 - 2¹ = 51859 is a prime.

It is a Curzon number.

51861 is a lucky number.

It is a nialpdrome in base 16.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 51861.

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 7 ways as a sum of consecutive naturals, for example, 31 + ... + 323.

It is an arithmetic number, because the mean of its divisors is an integer number (8820).

2⁵¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

51861 is a deficient number, since it is larger than the sum of its proper divisors (18699).

51861 is a wasteful number, since it uses less digits than its factorization.

51861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 355.

The product of its digits is 240, while the sum is 21.

The square root of 51861 is about 227.7301034119. The cubic root of 51861 is about 37.2918242592.

The spelling of 51861 in words is "fifty-one thousand, eight hundred sixty-one".