51391 has 4 divisors (see below), whose sum is σ = 54432. Its totient is φ = 48352.

The previous prime is 51383. The next prime is 51407. The reversal of 51391 is 19315.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19315 = 5 ⋅3863.

It is a cyclic number.

It is not a de Polignac number, because 51391 - 2³ = 51383 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

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 (51341) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1495 + ... + 1528.

It is an arithmetic number, because the mean of its divisors is an integer number (13608).

2⁵¹³⁹¹ is an apocalyptic number.

51391 is a deficient number, since it is larger than the sum of its proper divisors (3041).

51391 is a wasteful number, since it uses less digits than its factorization.

51391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3040.

The product of its digits is 135, while the sum is 19.

The square root of 51391 is about 226.6958314570. The cubic root of 51391 is about 37.1788275095.

The spelling of 51391 in words is "fifty-one thousand, three hundred ninety-one".