721809113 has 4 divisors (see below), whose sum is σ = 723060660. Its totient is φ = 720557568.

The previous prime is 721809089. The next prime is 721809119. The reversal of 721809113 is 311908127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 311908127 = 53 ⋅5885059.

It can be written as a sum of positive squares in 2 ways, for example, as 711395584 + 10413529 = 26672^2 + 3227^2 .

It is a cyclic number.

It is not a de Polignac number, because 721809113 - 2¹² = 721805017 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721809113.

It is not an unprimeable number, because it can be changed into a prime (721809119) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 624908 + ... + 626061.

It is an arithmetic number, because the mean of its divisors is an integer number (180765165).

Almost surely, 2^721809113 is an apocalyptic number.

It is an amenable number.

721809113 is a deficient number, since it is larger than the sum of its proper divisors (1251547).

721809113 is a wasteful number, since it uses less digits than its factorization.

721809113 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1251546.

The product of its (nonzero) digits is 3024, while the sum is 32.

The square root of 721809113 is about 26866.5054110132. The cubic root of 721809113 is about 897.0310036358.

The spelling of 721809113 in words is "seven hundred twenty-one million, eight hundred nine thousand, one hundred thirteen".