51998 has 4 divisors (see below), whose sum is σ = 78000. Its totient is φ = 25998.

The previous prime is 51991. The next prime is 52009. The reversal of 51998 is 89915.

It is a semiprime because it is the product of two primes.

It is an Ulam number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51991) by changing a digit.

51998 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12998 + ... + 13001.

It is an arithmetic number, because the mean of its divisors is an integer number (19500).

2⁵¹⁹⁹⁸ is an apocalyptic number.

51998 is a deficient number, since it is larger than the sum of its proper divisors (26002).

51998 is a wasteful number, since it uses less digits than its factorization.

51998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26001.

The product of its digits is 3240, while the sum is 32.

The square root of 51998 is about 228.0306996876. The cubic root of 51998 is about 37.3246330350.

The spelling of 51998 in words is "fifty-one thousand, nine hundred ninety-eight".