721489621 has 4 divisors (see below), whose sum is σ = 736840512. Its totient is φ = 706138732.

The previous prime is 721489609. The next prime is 721489633. The reversal of 721489621 is 126984127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (721489609) and next prime (721489633).

It is a cyclic number.

It is not a de Polignac number, because 721489621 - 2⁷ = 721489493 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721489651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7675375 + ... + 7675468.

It is an arithmetic number, because the mean of its divisors is an integer number (184210128).

Almost surely, 2^721489621 is an apocalyptic number.

It is an amenable number.

721489621 is a deficient number, since it is larger than the sum of its proper divisors (15350891).

721489621 is a wasteful number, since it uses less digits than its factorization.

721489621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15350890.

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

The square root of 721489621 is about 26860.5588363310. The cubic root of 721489621 is about 896.8986341403.

The spelling of 721489621 in words is "seven hundred twenty-one million, four hundred eighty-nine thousand, six hundred twenty-one".