721680 has 80 divisors (see below), whose sum is σ = 2333184. Its totient is φ = 184320.

The previous prime is 721663. The next prime is 721687. The reversal of 721680 is 86127.

721680 = T₈ + T₉ + ... + T₁₆₂.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 721680.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721687) 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, 7392 + ... + 7488.

2⁷²¹⁶⁸⁰ 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 721680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1166592).

721680 is an abundant number, since it is smaller than the sum of its proper divisors (1611504).

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

721680 is a wasteful number, since it uses less digits than its factorization.

721680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 138 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 721680 is about 849.5175101197. The cubic root of 721680 is about 89.6977515224.

The spelling of 721680 in words is "seven hundred twenty-one thousand, six hundred eighty".