51181921 has 6 divisors (see below), whose sum is σ = 59538210. Its totient is φ = 43870176.

The previous prime is 51181909. The next prime is 51181937. The reversal of 51181921 is 12918115.

51181921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 46771921 + 4410000 = 6839^2 + 2100^2 .

It is not a de Polignac number, because 51181921 - 2¹⁷ = 51050849 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51181921.

It is not an unprimeable number, because it can be changed into a prime (51181021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 522216 + ... + 522313.

It is an arithmetic number, because the mean of its divisors is an integer number (9923035).

Almost surely, 2^51181921 is an apocalyptic number.

It is an amenable number.

51181921 is a deficient number, since it is larger than the sum of its proper divisors (8356289).

51181921 is a wasteful number, since it uses less digits than its factorization.

51181921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1044543 (or 1044536 counting only the distinct ones).

The product of its digits is 720, while the sum is 28.

The square root of 51181921 is about 7154.1541079292. The cubic root of 51181921 is about 371.2833956664.

The spelling of 51181921 in words is "fifty-one million, one hundred eighty-one thousand, nine hundred twenty-one".