51315721 has 2 divisors, whose sum is σ = 51315722. Its totient is φ = 51315720.

The previous prime is 51315683. The next prime is 51315739. The reversal of 51315721 is 12751315.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48720400 + 2595321 = 6980^2 + 1611^2 .

It is a cyclic number.

It is not a de Polignac number, because 51315721 - 2¹⁵ = 51282953 is a prime.

It is not a weakly prime, because it can be changed into another prime (51315521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25657860 + 25657861.

It is an arithmetic number, because the mean of its divisors is an integer number (25657861).

Almost surely, 2^51315721 is an apocalyptic number.

It is an amenable number.

51315721 is a deficient number, since it is larger than the sum of its proper divisors (1).

51315721 is an equidigital number, since it uses as much as digits as its factorization.

51315721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1050, while the sum is 25.

The square root of 51315721 is about 7163.4992147693. The cubic root of 51315721 is about 371.6066510327.

The spelling of 51315721 in words is "fifty-one million, three hundred fifteen thousand, seven hundred twenty-one".