721440805 has 8 divisors (see below), whose sum is σ = 868811544. Its totient is φ = 575097600.

The previous prime is 721440787. The next prime is 721440809. The reversal of 721440805 is 508044127.

It can be written as a sum of positive squares in 4 ways, for example, as 40335201 + 681105604 = 6351^2 + 26098^2 .

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

It is not a de Polignac number, because 721440805 - 2¹⁷ = 721309733 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 (721440809) 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, 255336 + ... + 258145.

It is an arithmetic number, because the mean of its divisors is an integer number (108601443).

Almost surely, 2^721440805 is an apocalyptic number.

It is an amenable number.

721440805 is a deficient number, since it is larger than the sum of its proper divisors (147370739).

721440805 is a wasteful number, since it uses less digits than its factorization.

721440805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 513767.

The product of its (nonzero) digits is 8960, while the sum is 31.

The square root of 721440805 is about 26859.6501280266. The cubic root of 721440805 is about 896.8784056251.

The spelling of 721440805 in words is "seven hundred twenty-one million, four hundred forty thousand, eight hundred five".