721616565 has 16 divisors (see below), whose sum is σ = 1156192128. Its totient is φ = 384326976.

The previous prime is 721616549. The next prime is 721616579. The reversal of 721616565 is 565616127.

It is not a de Polignac number, because 721616565 - 2⁴ = 721616549 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 22182 + ... + 43991.

It is an arithmetic number, because the mean of its divisors is an integer number (72262008).

Almost surely, 2^721616565 is an apocalyptic number.

It is an amenable number.

721616565 is a deficient number, since it is larger than the sum of its proper divisors (434575563).

721616565 is a wasteful number, since it uses less digits than its factorization.

721616565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66908.

The product of its digits is 75600, while the sum is 39.

The square root of 721616565 is about 26862.9217509935. The cubic root of 721616565 is about 896.9512332907.

The spelling of 721616565 in words is "seven hundred twenty-one million, six hundred sixteen thousand, five hundred sixty-five".