51821 has 8 divisors (see below), whose sum is σ = 64704.
Its totient is φ = 40320.
The previous prime is 51817. The next prime is 51827. The reversal of 51821 is 12815.
It can be divided in two parts, 518 and 21, that multiplied together give a triangular number (10878 = T147).
It is a sphenic number, since it is the product of 3 distinct primes.
It is not a de Polignac number, because 51821 - 22 = 51817 is a prime.
It is a Duffinian number.
It is a Curzon number.
It is a self number, because there is not a number n which added to its sum of digits gives 51821.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (51827) 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, 260 + ... + 413.
It is an arithmetic number, because the mean of its divisors is an integer number (8088).
251821 is an apocalyptic number.
It is an amenable number.
51821 is a deficient number, since it is larger than the sum of its proper divisors (12883).
51821 is a wasteful number, since it uses less digits than its factorization.
51821 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 691.
The product of its digits is 80, while the sum is 17.
The square root of 51821 is about 227.6422632114.
The cubic root of 51821 is about 37.2822341585.
The spelling of 51821 in words is "fifty-one thousand, eight hundred twenty-one".