660721655171 has 4 divisors (see below), whose sum is σ = 661313170752. Its totient is φ = 660130139592.

The previous prime is 660721655159. The next prime is 660721655177. The reversal of 660721655171 is 171556127066.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-660721655171 is a prime.

It is a super-2 number, since 2×660721655171² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (660721655177) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 295756115 + ... + 295758348.

It is an arithmetic number, because the mean of its divisors is an integer number (165328292688).

Almost surely, 2^660721655171 is an apocalyptic number.

660721655171 is a deficient number, since it is larger than the sum of its proper divisors (591515581).

660721655171 is a wasteful number, since it uses less digits than its factorization.

660721655171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 591515580.

The product of its (nonzero) digits is 529200, while the sum is 47.

The spelling of 660721655171 in words is "six hundred sixty billion, seven hundred twenty-one million, six hundred fifty-five thousand, one hundred seventy-one".