721660 has 12 divisors (see below), whose sum is σ = 1515528. Its totient is φ = 288656.

The previous prime is 721631. The next prime is 721661. The reversal of 721660 is 66127.

721660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18022 + ... + 18061.

It is an arithmetic number, because the mean of its divisors is an integer number (126294).

2⁷²¹⁶⁶⁰ is an apocalyptic number.

It is an amenable number.

721660 is an abundant number, since it is smaller than the sum of its proper divisors (793868).

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

721660 is a wasteful number, since it uses less digits than its factorization.

721660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36092 (or 36090 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 721660 is about 849.5057386504. The cubic root of 721660 is about 89.6969229134.

Adding to 721660 its reverse (66127), we get a palindrome (787787).

The spelling of 721660 in words is "seven hundred twenty-one thousand, six hundred sixty".