661841385421056 has 288 divisors, whose sum is σ = 1876078178956800. Its totient is φ = 206542815805440.

The previous prime is 661841385421049. The next prime is 661841385421057. The reversal of 661841385421056 is 650124583148166.

It is not an unprimeable number, because it can be changed into a prime (661841385421057) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 638071491 + ... + 639107901.

It is an arithmetic number, because the mean of its divisors is an integer number (6514160343600).

Almost surely, 2^{661841385421056} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661841385421056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (938039089478400).

661841385421056 is an abundant number, since it is smaller than the sum of its proper divisors (1214236793535744).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661841385421056 is a wasteful number, since it uses less digits than its factorization.

661841385421056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1036965 (or 1036951 counting only the distinct ones).

The product of its (nonzero) digits is 33177600, while the sum is 60.

The spelling of 661841385421056 in words is "six hundred sixty-one trillion, eight hundred forty-one billion, three hundred eighty-five million, four hundred twenty-one thousand, fifty-six".