721776 has 40 divisors (see below), whose sum is σ = 2035584. Its totient is φ = 218560.

The previous prime is 721739. The next prime is 721783. The reversal of 721776 is 677127.

It is a happy number.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

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 721776.

It is an unprimeable number.

721776 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156 + ... + 1211.

2⁷²¹⁷⁷⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1017792).

721776 is an abundant number, since it is smaller than the sum of its proper divisors (1313808).

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

721776 is a wasteful number, since it uses less digits than its factorization.

721776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1389 (or 1383 counting only the distinct ones).

The product of its digits is 4116, while the sum is 30.

The square root of 721776 is about 849.5740109019. The cubic root of 721776 is about 89.7017286324.

The spelling of 721776 in words is "seven hundred twenty-one thousand, seven hundred seventy-six".