661568284421 has 16 divisors (see below), whose sum is σ = 722530672128. Its totient is φ = 600742892400.

The previous prime is 661568284409. The next prime is 661568284439. The reversal of 661568284421 is 124482865166.

It is a cyclic number.

It is not a de Polignac number, because 661568284421 - 2⁶ = 661568284357 is a prime.

It is a super-5 number, since 5×661568284421⁵ (a number of 60 digits) contains 55555 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661568284451) 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, 50390960 + ... + 50404086.

It is an arithmetic number, because the mean of its divisors is an integer number (45158167008).

Almost surely, 2^661568284421 is an apocalyptic number.

It is an amenable number.

661568284421 is a deficient number, since it is larger than the sum of its proper divisors (60962387707).

661568284421 is a wasteful number, since it uses less digits than its factorization.

661568284421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17992.

The product of its digits is 4423680, while the sum is 53.

The spelling of 661568284421 in words is "six hundred sixty-one billion, five hundred sixty-eight million, two hundred eighty-four thousand, four hundred twenty-one".