51816321721 has 2 divisors, whose sum is σ = 51816321722. Its totient is φ = 51816321720.

The previous prime is 51816321703. The next prime is 51816321763. The reversal of 51816321721 is 12712361815.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50180928121 + 1635393600 = 224011^2 + 40440^2 .

It is a cyclic number.

It is not a de Polignac number, because 51816321721 - 2⁹ = 51816321209 is a prime.

It is not a weakly prime, because it can be changed into another prime (51816327721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25908160860 + 25908160861.

It is an arithmetic number, because the mean of its divisors is an integer number (25908160861).

Almost surely, 2^51816321721 is an apocalyptic number.

It is an amenable number.

51816321721 is a deficient number, since it is larger than the sum of its proper divisors (1).

51816321721 is an equidigital number, since it uses as much as digits as its factorization.

51816321721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 37.

The spelling of 51816321721 in words is "fifty-one billion, eight hundred sixteen million, three hundred twenty-one thousand, seven hundred twenty-one".