51381 has 16 divisors (see below), whose sum is σ = 83520. Its totient is φ = 30960.

The previous prime is 51361. The next prime is 51383. The reversal of 51381 is 18315.

Added to its reverse (18315) it gives a square (69696 = 264²).

It is a happy number.

51381 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 not a de Polignac number, because 51381 - 2⁵ = 51349 is a prime.

It is a super-2 number, since 2×51381² = 5280014322, which contains 22 as substring.

It is a Curzon number.

It is a plaindrome in base 12.

It is a nialpdrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51383) 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, 211 + ... + 383.

It is an arithmetic number, because the mean of its divisors is an integer number (5220).

2⁵¹³⁸¹ is an apocalyptic number.

It is an amenable number.

51381 is a deficient number, since it is larger than the sum of its proper divisors (32139).

51381 is a wasteful number, since it uses less digits than its factorization.

51381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 187 counting only the distinct ones).

The product of its digits is 120, while the sum is 18.

The square root of 51381 is about 226.6737743984. The cubic root of 51381 is about 37.1764158525.

Adding to 51381 its reverse (18315), we get a palindrome (69696).

The spelling of 51381 in words is "fifty-one thousand, three hundred eighty-one".