721616 has 40 divisors (see below), whose sum is σ = 1696320. Its totient is φ = 290304.

The previous prime is 721613. The next prime is 721619. The reversal of 721616 is 616127.

It is an interprime number because it is at equal distance from previous prime (721613) and next prime (721619).

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

It is a junction number, because it is equal to n+sod(n) for n = 721591 and 721600.

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 721616.

It is not an unprimeable number, because it can be changed into a prime (721613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1715 + ... + 2093.

It is an arithmetic number, because the mean of its divisors is an integer number (42408).

2⁷²¹⁶¹⁶ 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 721616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (848160).

721616 is an abundant number, since it is smaller than the sum of its proper divisors (974704).

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

721616 is a wasteful number, since it uses less digits than its factorization.

721616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 411 (or 405 counting only the distinct ones).

The product of its digits is 504, while the sum is 23.

The square root of 721616 is about 849.4798408438. The cubic root of 721616 is about 89.6950999197.

The spelling of 721616 in words is "seven hundred twenty-one thousand, six hundred sixteen".