51128521781 has 2 divisors, whose sum is σ = 51128521782. Its totient is φ = 51128521780.

The previous prime is 51128521753. The next prime is 51128521799. The reversal of 51128521781 is 18712582115.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43949348881 + 7179172900 = 209641^2 + 84730^2 .

It is a cyclic number.

It is not a de Polignac number, because 51128521781 - 2¹⁰ = 51128520757 is a prime.

It is a super-2 number, since 2×51128521781² (a number of 22 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51128521711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25564260890 + 25564260891.

It is an arithmetic number, because the mean of its divisors is an integer number (25564260891).

Almost surely, 2^51128521781 is an apocalyptic number.

It is an amenable number.

51128521781 is a deficient number, since it is larger than the sum of its proper divisors (1).

51128521781 is an equidigital number, since it uses as much as digits as its factorization.

51128521781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 44800, while the sum is 41.

The spelling of 51128521781 in words is "fifty-one billion, one hundred twenty-eight million, five hundred twenty-one thousand, seven hundred eighty-one".