721648 has 40 divisors (see below), whose sum is σ = 1526688. Its totient is φ = 329472.

The previous prime is 721631. The next prime is 721661. The reversal of 721648 is 846127.

It is a congruent number.

It is an unprimeable number.

721648 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, 13590 + ... + 13642.

2⁷²¹⁶⁴⁸ 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 721648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (763344).

721648 is an abundant number, since it is smaller than the sum of its proper divisors (805040).

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

721648 is a wasteful number, since it uses less digits than its factorization.

721648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121 (or 115 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 721648 is about 849.4986756906. The cubic root of 721648 is about 89.6964257406.

It can be divided in two parts, 721 and 648, that added together give a square (1369 = 37²).

The spelling of 721648 in words is "seven hundred twenty-one thousand, six hundred forty-eight".