721021640 has 32 divisors (see below), whose sum is σ = 1637470080. Its totient is φ = 285711552.

The previous prime is 721021607. The next prime is 721021643. The reversal of 721021640 is 46120127.

It is not an unprimeable number, because it can be changed into a prime (721021643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79952 + ... + 88511.

It is an arithmetic number, because the mean of its divisors is an integer number (51170940).

Almost surely, 2^721021640 is an apocalyptic number.

It is an amenable number.

721021640 is an abundant number, since it is smaller than the sum of its proper divisors (916448440).

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

721021640 is a wasteful number, since it uses less digits than its factorization.

721021640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168581 (or 168577 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 721021640 is about 26851.8461190288. The cubic root of 721021640 is about 896.7046732522.

Adding to 721021640 its reverse (46120127), we get a palindrome (767141767).

The spelling of 721021640 in words is "seven hundred twenty-one million, twenty-one thousand, six hundred forty".