661542865984 has 336 divisors, whose sum is σ = 1797521302080. Its totient is φ = 237457059840.

The previous prime is 661542865943. The next prime is 661542865999. The reversal of 661542865984 is 489568245166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (64).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 303598207 + ... + 303600385.

It is an arithmetic number, because the mean of its divisors is an integer number (5349765780).

Almost surely, 2^661542865984 is an apocalyptic number.

661542865984 is a gapful number since it is divisible by the number (64) 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 661542865984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (898760651040).

661542865984 is an abundant number, since it is smaller than the sum of its proper divisors (1135978436096).

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

661542865984 is a wasteful number, since it uses less digits than its factorization.

661542865984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2906 (or 2889 counting only the distinct ones).

The product of its digits is 99532800, while the sum is 64.

The spelling of 661542865984 in words is "six hundred sixty-one billion, five hundred forty-two million, eight hundred sixty-five thousand, nine hundred eighty-four".