721163521 has 8 divisors (see below), whose sum is σ = 777682304. Its totient is φ = 664794000.

The previous prime is 721163501. The next prime is 721163557. The reversal of 721163521 is 125361127.

It is a happy number.

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

It is not a de Polignac number, because 721163521 - 2⁵ = 721163489 is a prime.

It is a super-2 number, since 2×721163521² = 1040153648042234882, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721163521.

It is not an unprimeable number, because it can be changed into a prime (721163501) 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 7 ways as a sum of consecutive naturals, for example, 27171 + ... + 46696.

It is an arithmetic number, because the mean of its divisors is an integer number (97210288).

Almost surely, 2^721163521 is an apocalyptic number.

It is an amenable number.

721163521 is a deficient number, since it is larger than the sum of its proper divisors (56518783).

721163521 is a wasteful number, since it uses less digits than its factorization.

721163521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74631.

The product of its digits is 2520, while the sum is 28.

The square root of 721163521 is about 26854.4879117067. The cubic root of 721163521 is about 896.7634865641.

The spelling of 721163521 in words is "seven hundred twenty-one million, one hundred sixty-three thousand, five hundred twenty-one".