51085378921 has 2 divisors, whose sum is σ = 51085378922. Its totient is φ = 51085378920.

The previous prime is 51085378873. The next prime is 51085378933. The reversal of 51085378921 is 12987358015.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50440218921 + 645160000 = 224589^2 + 25400^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51085378921 is a prime.

It is a super-2 number, since 2×51085378921² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (51085378121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25542689460 + 25542689461.

It is an arithmetic number, because the mean of its divisors is an integer number (25542689461).

Almost surely, 2^51085378921 is an apocalyptic number.

It is an amenable number.

51085378921 is a deficient number, since it is larger than the sum of its proper divisors (1).

51085378921 is an equidigital number, since it uses as much as digits as its factorization.

51085378921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 604800, while the sum is 49.

The spelling of 51085378921 in words is "fifty-one billion, eighty-five million, three hundred seventy-eight thousand, nine hundred twenty-one".