721643715856 has 80 divisors (see below), whose sum is σ = 1663974570240. Its totient is φ = 296633433600.

The previous prime is 721643715853. The next prime is 721643715887. The reversal of 721643715856 is 658517346127.

It is a junction number, because it is equal to n+sod(n) for n = 721643715797 and 721643715806.

It is not an unprimeable number, because it can be changed into a prime (721643715853) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 245251 + ... + 1226146.

It is an arithmetic number, because the mean of its divisors is an integer number (20799682128).

Almost surely, 2^721643715856 is an apocalyptic number.

It is an amenable number.

721643715856 is an abundant number, since it is smaller than the sum of its proper divisors (942330854384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721643715856 is a wasteful number, since it uses less digits than its factorization.

721643715856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1471592 (or 1471586 counting only the distinct ones).

The product of its digits is 8467200, while the sum is 55.

The spelling of 721643715856 in words is "seven hundred twenty-one billion, six hundred forty-three million, seven hundred fifteen thousand, eight hundred fifty-six".