51091921 has 2 divisors, whose sum is σ = 51091922. Its totient is φ = 51091920.

The previous prime is 51091913. The next prime is 51091949. The reversal of 51091921 is 12919015.

51091921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (51091949) can be obtained adding 51091921 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 32901696 + 18190225 = 5736^2 + 4265^2 .

It is a cyclic number.

It is not a de Polignac number, because 51091921 - 2³ = 51091913 is a prime.

It is a super-2 number, since 2×51091921² = 5220768782940482, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 51091921.

It is not a weakly prime, because it can be changed into another prime (51091981) 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 as a sum of consecutive naturals, namely, 25545960 + 25545961.

It is an arithmetic number, because the mean of its divisors is an integer number (25545961).

Almost surely, 2^51091921 is an apocalyptic number.

It is an amenable number.

51091921 is a deficient number, since it is larger than the sum of its proper divisors (1).

51091921 is an equidigital number, since it uses as much as digits as its factorization.

51091921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 810, while the sum is 28.

The square root of 51091921 is about 7147.8612885254. The cubic root of 51091921 is about 371.0656422721.

The spelling of 51091921 in words is "fifty-one million, ninety-one thousand, nine hundred twenty-one".