721621613 has 4 divisors (see below), whose sum is σ = 723972480. Its totient is φ = 719270748.

The previous prime is 721621603. The next prime is 721621633. The reversal of 721621613 is 316126127.

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 721621613 - 2⁸ = 721621357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721621603) 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, 1174973 + ... + 1175586.

It is an arithmetic number, because the mean of its divisors is an integer number (180993120).

Almost surely, 2^721621613 is an apocalyptic number.

It is an amenable number.

721621613 is a deficient number, since it is larger than the sum of its proper divisors (2350867).

721621613 is a wasteful number, since it uses less digits than its factorization.

721621613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2350866.

The product of its digits is 3024, while the sum is 29.

The square root of 721621613 is about 26863.0157093354. The cubic root of 721621613 is about 896.9533247982.

The spelling of 721621613 in words is "seven hundred twenty-one million, six hundred twenty-one thousand, six hundred thirteen".