721512317 has 4 divisors (see below), whose sum is σ = 763954236. Its totient is φ = 679070400.

The previous prime is 721512299. The next prime is 721512349. The reversal of 721512317 is 713215127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 713215127 = 17 ⋅41953831.

It can be written as a sum of positive squares in 2 ways, for example, as 488675236 + 232837081 = 22106^2 + 15259^2 .

It is a cyclic number.

It is not a de Polignac number, because 721512317 - 2²⁸ = 453076861 is a prime.

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 721512317.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721512367) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21220934 + ... + 21220967.

It is an arithmetic number, because the mean of its divisors is an integer number (190988559).

Almost surely, 2^721512317 is an apocalyptic number.

It is an amenable number.

721512317 is a deficient number, since it is larger than the sum of its proper divisors (42441919).

721512317 is a wasteful number, since it uses less digits than its factorization.

721512317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42441918.

The product of its digits is 2940, while the sum is 29.

The square root of 721512317 is about 26860.9813111882. The cubic root of 721512317 is about 896.9080386636.

The spelling of 721512317 in words is "seven hundred twenty-one million, five hundred twelve thousand, three hundred seventeen".