661560665221 has 8 divisors (see below), whose sum is σ = 677719373184. Its totient is φ = 645403056480.

The previous prime is 661560665179. The next prime is 661560665261. The reversal of 661560665221 is 122566065166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661560665221 - 2¹¹ = 661560663173 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 (661560665261) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1016820 + ... + 1535266.

It is an arithmetic number, because the mean of its divisors is an integer number (84714921648).

Almost surely, 2^661560665221 is an apocalyptic number.

It is an amenable number.

661560665221 is a deficient number, since it is larger than the sum of its proper divisors (16158707963).

661560665221 is a wasteful number, since it uses less digits than its factorization.

661560665221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549611.

The product of its (nonzero) digits is 777600, while the sum is 46.

The spelling of 661560665221 in words is "six hundred sixty-one billion, five hundred sixty million, six hundred sixty-five thousand, two hundred twenty-one".