51200021 has 4 divisors (see below), whose sum is σ = 52448844. Its totient is φ = 49951200.

The previous prime is 51199991. The next prime is 51200027. The reversal of 51200021 is 12000215.

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 3783025 + 47416996 = 1945^2 + 6886^2 .

It is a cyclic number.

It is not a de Polignac number, because 51200021 - 2⁶ = 51199957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 51199975 and 51200011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51200027) 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, 624350 + ... + 624431.

It is an arithmetic number, because the mean of its divisors is an integer number (13112211).

Almost surely, 2^51200021 is an apocalyptic number.

It is an amenable number.

51200021 is a deficient number, since it is larger than the sum of its proper divisors (1248823).

51200021 is a wasteful number, since it uses less digits than its factorization.

51200021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1248822.

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 51200021 is about 7155.4189954188. The cubic root of 51200021 is about 371.3271574564.

Adding to 51200021 its reverse (12000215), we get a palindrome (63200236).

The spelling of 51200021 in words is "fifty-one million, two hundred thousand, twenty-one".