721515121 has 2 divisors, whose sum is σ = 721515122. Its totient is φ = 721515120.

The previous prime is 721515097. The next prime is 721515127. The reversal of 721515121 is 121515127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 590733025 + 130782096 = 24305^2 + 11436^2 .

It is a cyclic number.

It is not a de Polignac number, because 721515121 - 2²⁷ = 587297393 is a prime.

It is a nialpdrome in base 13.

It is not a weakly prime, because it can be changed into another prime (721515127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360757560 + 360757561.

It is an arithmetic number, because the mean of its divisors is an integer number (360757561).

Almost surely, 2^721515121 is an apocalyptic number.

It is an amenable number.

721515121 is a deficient number, since it is larger than the sum of its proper divisors (1).

721515121 is an equidigital number, since it uses as much as digits as its factorization.

721515121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 700, while the sum is 25.

The square root of 721515121 is about 26861.0335058054. The cubic root of 721515121 is about 896.9092005412.

The spelling of 721515121 in words is "seven hundred twenty-one million, five hundred fifteen thousand, one hundred twenty-one".