721507221 has 12 divisors (see below), whose sum is σ = 1042542540. Its totient is φ = 480836160.

The previous prime is 721507219. The next prime is 721507229. The reversal of 721507221 is 122705127.

It can be written as a sum of positive squares in 2 ways, for example, as 208484721 + 513022500 = 14439^2 + 22650^2 .

It is not a de Polignac number, because 721507221 - 2¹ = 721507219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721507229) 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 in 11 ways as a sum of consecutive naturals, for example, 16545 + ... + 41433.

It is an arithmetic number, because the mean of its divisors is an integer number (86878545).

Almost surely, 2^721507221 is an apocalyptic number.

It is an amenable number.

721507221 is a deficient number, since it is larger than the sum of its proper divisors (321035319).

721507221 is a wasteful number, since it uses less digits than its factorization.

721507221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28116 (or 28113 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 721507221 is about 26860.8864522376. The cubic root of 721507221 is about 896.9059270554.

The spelling of 721507221 in words is "seven hundred twenty-one million, five hundred seven thousand, two hundred twenty-one".