51805021 has 4 divisors (see below), whose sum is σ = 52318044. Its totient is φ = 51292000.

The previous prime is 51804997. The next prime is 51805051. The reversal of 51805021 is 12050815.

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

It can be written as a sum of positive squares in 2 ways, for example, as 23863225 + 27941796 = 4885^2 + 5286^2 .

It is a cyclic number.

It is not a de Polignac number, because 51805021 - 2⁵ = 51804989 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 51804983 and 51805001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51805051) 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, 256360 + ... + 256561.

It is an arithmetic number, because the mean of its divisors is an integer number (13079511).

Almost surely, 2^51805021 is an apocalyptic number.

It is an amenable number.

51805021 is a deficient number, since it is larger than the sum of its proper divisors (513023).

51805021 is a wasteful number, since it uses less digits than its factorization.

51805021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 513022.

The product of its (nonzero) digits is 400, while the sum is 22.

The square root of 51805021 is about 7197.5704928816. The cubic root of 51805021 is about 372.7840177355.

Adding to 51805021 its reverse (12050815), we get a palindrome (63855836).

It can be divided in two parts, 5180 and 5021, that added together give a palindrome (10201).

The spelling of 51805021 in words is "fifty-one million, eight hundred five thousand, twenty-one".