721421689 has 8 divisors (see below), whose sum is σ = 736085448. Its totient is φ = 706905600.

The previous prime is 721421681. The next prime is 721421737. The reversal of 721421689 is 986124127.

It can be written as a sum of positive squares in 4 ways, for example, as 511664400 + 209757289 = 22620^2 + 14483^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 721421689 - 2³ = 721421681 is a prime.

It is a super-2 number, since 2×721421689² = 1040898506719225442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721421681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27022 + ... + 46615.

It is an arithmetic number, because the mean of its divisors is an integer number (92010681).

Almost surely, 2^721421689 is an apocalyptic number.

It is an amenable number.

721421689 is a deficient number, since it is larger than the sum of its proper divisors (14663759).

721421689 is a wasteful number, since it uses less digits than its factorization.

721421689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73835.

The product of its digits is 48384, while the sum is 40.

The square root of 721421689 is about 26859.2942759113. The cubic root of 721421689 is about 896.8704840332.

The spelling of 721421689 in words is "seven hundred twenty-one million, four hundred twenty-one thousand, six hundred eighty-nine".