661165055321 has 16 divisors (see below), whose sum is σ = 673508858880. Its totient is φ = 648947529360.

The previous prime is 661165055297. The next prime is 661165055323. The reversal of 661165055321 is 123550561166.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661165055321 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661165055323) 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, 11074970 + ... + 11134508.

It is an arithmetic number, because the mean of its divisors is an integer number (42094303680).

Almost surely, 2^661165055321 is an apocalyptic number.

It is an amenable number.

661165055321 is a deficient number, since it is larger than the sum of its proper divisors (12343803559).

661165055321 is a wasteful number, since it uses less digits than its factorization.

661165055321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60596.

The product of its (nonzero) digits is 162000, while the sum is 41.

The spelling of 661165055321 in words is "six hundred sixty-one billion, one hundred sixty-five million, fifty-five thousand, three hundred twenty-one".