661105566 has 192 divisors, whose sum is σ = 1720922112. Its totient is φ = 181440000.

The previous prime is 661105553. The next prime is 661105567. The reversal of 661105566 is 665501166.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 661105566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661105567) by changing a digit.

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 95 ways as a sum of consecutive naturals, for example, 9311311 + ... + 9311381.

It is an arithmetic number, because the mean of its divisors is an integer number (8963136).

Almost surely, 2^661105566 is an apocalyptic number.

661105566 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 661105566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (860461056).

661105566 is an abundant number, since it is smaller than the sum of its proper divisors (1059816546).

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

661105566 is a wasteful number, since it uses less digits than its factorization.

661105566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 661105566 is about 25711.9732031597. The cubic root of 661105566 is about 871.1446447562.

The spelling of 661105566 in words is "six hundred sixty-one million, one hundred five thousand, five hundred sixty-six".