51021 has 6 divisors (see below), whose sum is σ = 73710. Its totient is φ = 34008.

The previous prime is 51001. The next prime is 51031. The reversal of 51021 is 12015.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 38025 + 12996 = 195^2 + 114^2 .

It is not a de Polignac number, because 51021 - 2⁵ = 50989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 5669 = 51021 / (5 + 1 + 0 + 2 + 1).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 50994 and 51012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51001) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2826 + ... + 2843.

It is an arithmetic number, because the mean of its divisors is an integer number (12285).

2⁵¹⁰²¹ is an apocalyptic number.

It is an amenable number.

51021 is a deficient number, since it is larger than the sum of its proper divisors (22689).

51021 is a wasteful number, since it uses less digits than its factorization.

51021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5675 (or 5672 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 9.

The square root of 51021 is about 225.8782858090. The cubic root of 51021 is about 37.0893869958.

Adding to 51021 its reverse (12015), we get a palindrome (63036).

The spelling of 51021 in words is "fifty-one thousand, twenty-one".