721643715855 has 24 divisors (see below), whose sum is σ = 1251934062288. Its totient is φ = 384542816256.

The previous prime is 721643715853. The next prime is 721643715887. The reversal of 721643715855 is 558517346127.

721643715855 is a `hidden beast` number, since 7 + 2 + 1 + 6 + 437 + 158 + 55 = 666.

It is not a de Polignac number, because 721643715855 - 2¹ = 721643715853 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721643715853) 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 23 ways as a sum of consecutive naturals, for example, 6902377 + ... + 7006146.

It is an arithmetic number, because the mean of its divisors is an integer number (52163919262).

Almost surely, 2^721643715855 is an apocalyptic number.

721643715855 is a deficient number, since it is larger than the sum of its proper divisors (530290346433).

721643715855 is a wasteful number, since it uses less digits than its factorization.

721643715855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13909687 (or 13909684 counting only the distinct ones).

The product of its digits is 7056000, while the sum is 54.

The spelling of 721643715855 in words is "seven hundred twenty-one billion, six hundred forty-three million, seven hundred fifteen thousand, eight hundred fifty-five".