51021721 has 2 divisors, whose sum is σ = 51021722. Its totient is φ = 51021720.

The previous prime is 51021713. The next prime is 51021769. The reversal of 51021721 is 12712015.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50922496 + 99225 = 7136^2 + 315^2 .

It is a cyclic number.

It is not a de Polignac number, because 51021721 - 2³ = 51021713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (51021781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25510860 + 25510861.

It is an arithmetic number, because the mean of its divisors is an integer number (25510861).

Almost surely, 2^51021721 is an apocalyptic number.

It is an amenable number.

51021721 is a deficient number, since it is larger than the sum of its proper divisors (1).

51021721 is an equidigital number, since it uses as much as digits as its factorization.

51021721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 51021721 is about 7142.9490408374. The cubic root of 51021721 is about 370.8956170378.

Adding to 51021721 its reverse (12712015), we get a palindrome (63733736).

The spelling of 51021721 in words is "fifty-one million, twenty-one thousand, seven hundred twenty-one".