721665612317017 has 4 divisors (see below), whose sum is σ = 721668813131520. Its totient is φ = 721662411502516.

The previous prime is 721665612316963. The next prime is 721665612317063. The reversal of 721665612317017 is 710713216566127.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 721665612317017 - 2⁷ = 721665612316889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721665612417017) 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, 1600069033 + ... + 1600519990.

It is an arithmetic number, because the mean of its divisors is an integer number (180417203282880).

Almost surely, 2^{721665612317017} is an apocalyptic number.

It is an amenable number.

721665612317017 is a deficient number, since it is larger than the sum of its proper divisors (3200814503).

721665612317017 is a wasteful number, since it uses less digits than its factorization.

721665612317017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3200814502.

The product of its (nonzero) digits is 4445280, while the sum is 55.

The spelling of 721665612317017 in words is "seven hundred twenty-one trillion, six hundred sixty-five billion, six hundred twelve million, three hundred seventeen thousand, seventeen".