661578546720 has 768 divisors, whose sum is σ = 2683091755008. Its totient is φ = 133183733760.

The previous prime is 661578546703. The next prime is 661578546737. The reversal of 661578546720 is 27645875166.

It is an interprime number because it is at equal distance from previous prime (661578546703) and next prime (661578546737).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 694205764 + ... + 694206716.

It is an arithmetic number, because the mean of its divisors is an integer number (3493609056).

Almost surely, 2^661578546720 is an apocalyptic number.

661578546720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661578546720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1341545877504).

661578546720 is an abundant number, since it is smaller than the sum of its proper divisors (2021513208288).

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

661578546720 is a wasteful number, since it uses less digits than its factorization.

661578546720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1705 (or 1697 counting only the distinct ones).

The product of its (nonzero) digits is 16934400, while the sum is 57.

The spelling of 661578546720 in words is "six hundred sixty-one billion, five hundred seventy-eight million, five hundred forty-six thousand, seven hundred twenty".