721913 has 6 divisors (see below), whose sum is σ = 738654. Its totient is φ = 705536.

The previous prime is 721909. The next prime is 721921. The reversal of 721913 is 319127.

It can be written as a sum of positive squares in 3 ways, for example, as 478864 + 243049 = 692^2 + 493^2 .

It is not a de Polignac number, because 721913 - 2² = 721909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721913.

It is not an unprimeable number, because it can be changed into a prime (721013) 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 in 5 ways as a sum of consecutive naturals, for example, 2681 + ... + 2937.

It is an arithmetic number, because the mean of its divisors is an integer number (123109).

2⁷²¹⁹¹³ is an apocalyptic number.

It is an amenable number.

721913 is a deficient number, since it is larger than the sum of its proper divisors (16741).

721913 is an equidigital number, since it uses as much as digits as its factorization.

721913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363 (or 310 counting only the distinct ones).

The product of its digits is 378, while the sum is 23.

The square root of 721913 is about 849.6546357197. The cubic root of 721913 is about 89.7074036892.

The spelling of 721913 in words is "seven hundred twenty-one thousand, nine hundred thirteen".