721520 has 40 divisors (see below), whose sum is σ = 1740960. Its totient is φ = 277760.

The previous prime is 721499. The next prime is 721529. The reversal of 721520 is 25127.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×721520² = 1041182220800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721529) by changing a digit.

721520 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 2165 + ... + 2475.

It is an arithmetic number, because the mean of its divisors is an integer number (43524).

2⁷²¹⁵²⁰ 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 721520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (870480).

721520 is an abundant number, since it is smaller than the sum of its proper divisors (1019440).

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

721520 is a wasteful number, since it uses less digits than its factorization.

721520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 353 (or 347 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 721520 is about 849.4233337977. The cubic root of 721520 is about 89.6911222217.

Adding to 721520 its reverse (25127), we get a palindrome (746647).

The spelling of 721520 in words is "seven hundred twenty-one thousand, five hundred twenty".