661381562688 has 504 divisors, whose sum is σ = 2243956107456. Its totient is φ = 171290972160.

The previous prime is 661381562641. The next prime is 661381562741. The reversal of 661381562688 is 886265183166.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

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 71 ways as a sum of consecutive naturals, for example, 554384620 + ... + 554385812.

It is an arithmetic number, because the mean of its divisors is an integer number (4452293864).

Almost surely, 2^661381562688 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 661381562688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1121978053728).

661381562688 is an abundant number, since it is smaller than the sum of its proper divisors (1582574544768).

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

661381562688 is a wasteful number, since it uses less digits than its factorization.

661381562688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1731 (or 1703 counting only the distinct ones).

The product of its digits is 19906560, while the sum is 60.

The spelling of 661381562688 in words is "six hundred sixty-one billion, three hundred eighty-one million, five hundred sixty-two thousand, six hundred eighty-eight".