721516553 has 2 divisors, whose sum is σ = 721516554. Its totient is φ = 721516552.

The previous prime is 721516547. The next prime is 721516561. The reversal of 721516553 is 355615127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 695271424 + 26245129 = 26368^2 + 5123^2 .

It is a cyclic number.

It is not a de Polignac number, because 721516553 - 2⁸ = 721516297 is a prime.

It is a super-3 number, since 3×721516553³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (721516573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360758276 + 360758277.

It is an arithmetic number, because the mean of its divisors is an integer number (360758277).

Almost surely, 2^721516553 is an apocalyptic number.

It is an amenable number.

721516553 is a deficient number, since it is larger than the sum of its proper divisors (1).

721516553 is an equidigital number, since it uses as much as digits as its factorization.

721516553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31500, while the sum is 35.

The square root of 721516553 is about 26861.0601615052. The cubic root of 721516553 is about 896.9097939097.

The spelling of 721516553 in words is "seven hundred twenty-one million, five hundred sixteen thousand, five hundred fifty-three".