721620 has 72 divisors (see below), whose sum is σ = 2315040. Its totient is φ = 181440.

The previous prime is 721619. The next prime is 721621. The reversal of 721620 is 26127.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (721619) and next prime (721621).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 721593 and 721602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721621) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3315 + ... + 3525.

2⁷²¹⁶²⁰ 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 721620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1157520).

721620 is an abundant number, since it is smaller than the sum of its proper divisors (1593420).

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

721620 is a wasteful number, since it uses less digits than its factorization.

721620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 245 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 721620 is about 849.4821952225. The cubic root of 721620 is about 89.6952656495.

Adding to 721620 its reverse (26127), we get a palindrome (747747).

The spelling of 721620 in words is "seven hundred twenty-one thousand, six hundred twenty".