721519621 has 4 divisors (see below), whose sum is σ = 721834144. Its totient is φ = 721205100.

The previous prime is 721519619. The next prime is 721519657. The reversal of 721519621 is 126915127.

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 a cyclic number.

It is not a de Polignac number, because 721519621 - 2¹ = 721519619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721519691) 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, 153795 + ... + 158416.

It is an arithmetic number, because the mean of its divisors is an integer number (180458536).

Almost surely, 2^721519621 is an apocalyptic number.

It is an amenable number.

721519621 is a deficient number, since it is larger than the sum of its proper divisors (314523).

721519621 is a wasteful number, since it uses less digits than its factorization.

721519621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 314522.

The product of its digits is 7560, while the sum is 34.

The square root of 721519621 is about 26861.1172701360. The cubic root of 721519621 is about 896.9110651743.

The spelling of 721519621 in words is "seven hundred twenty-one million, five hundred nineteen thousand, six hundred twenty-one".