721243505 has 8 divisors (see below), whose sum is σ = 886602024. Its totient is φ = 562921600.

The previous prime is 721243483. The next prime is 721243507. The reversal of 721243505 is 505342127.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 63218401 + 658025104 = 7951^2 + 25652^2 .

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

It is not a de Polignac number, because 721243505 - 2¹⁰ = 721242481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721243507) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1758926 + ... + 1759335.

It is an arithmetic number, because the mean of its divisors is an integer number (110825253).

Almost surely, 2^721243505 is an apocalyptic number.

It is an amenable number.

721243505 is a deficient number, since it is larger than the sum of its proper divisors (165358519).

721243505 is a wasteful number, since it uses less digits than its factorization.

721243505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3518307.

The product of its (nonzero) digits is 8400, while the sum is 29.

The square root of 721243505 is about 26855.9770814618. The cubic root of 721243505 is about 896.7966385825.

The spelling of 721243505 in words is "seven hundred twenty-one million, two hundred forty-three thousand, five hundred five".