51990 has 16 divisors (see below), whose sum is σ = 124848. Its totient is φ = 13856.

The previous prime is 51977. The next prime is 51991. The reversal of 51990 is 9915.

It is a happy number.

51990 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 51990.

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 51990.

It is not an unprimeable number, because it can be changed into a prime (51991) 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, 837 + ... + 896.

It is an arithmetic number, because the mean of its divisors is an integer number (7803).

2⁵¹⁹⁹⁰ is an apocalyptic number.

51990 is an abundant number, since it is smaller than the sum of its proper divisors (72858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (62424).

51990 is a wasteful number, since it uses less digits than its factorization.

51990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1743.

The product of its (nonzero) digits is 405, while the sum is 24.

The square root of 51990 is about 228.0131575151. The cubic root of 51990 is about 37.3227187794.

The spelling of 51990 in words is "fifty-one thousand, nine hundred ninety".