721265605 has 16 divisors (see below), whose sum is σ = 905695344. Its totient is φ = 550817280.

The previous prime is 721265603. The next prime is 721265683. The reversal of 721265605 is 506562127.

It can be written as a sum of positive squares in 8 ways, for example, as 772641 + 720492964 = 879^2 + 26842^2 .

It is not a de Polignac number, because 721265605 - 2¹ = 721265603 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 (721265603) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26976 + ... + 46585.

It is an arithmetic number, because the mean of its divisors is an integer number (56605959).

Almost surely, 2^721265605 is an apocalyptic number.

It is an amenable number.

721265605 is a deficient number, since it is larger than the sum of its proper divisors (184429739).

721265605 is a wasteful number, since it uses less digits than its factorization.

721265605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73656.

The product of its (nonzero) digits is 25200, while the sum is 34.

The square root of 721265605 is about 26856.3885323399. The cubic root of 721265605 is about 896.8057982275.

The spelling of 721265605 in words is "seven hundred twenty-one million, two hundred sixty-five thousand, six hundred five".