66561588 has 108 divisors (see below), whose sum is σ = 184026752. Its totient is φ = 21014640.

The previous prime is 66561571. The next prime is 66561611. The reversal of 66561588 is 88516566.

66561588 is a `hidden beast` number, since 6 + 6 + 5 + 61 + 588 = 666.

It is a tau number, because it is divible by the number of its divisors (108).

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

Its product of digits (345600) is a multiple of the sum of its prime factors (144).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1416181 + ... + 1416227.

Almost surely, 2^66561588 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 66561588, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92013376).

66561588 is an abundant number, since it is smaller than the sum of its proper divisors (117465164).

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

66561588 is a wasteful number, since it uses less digits than its factorization.

66561588 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 83 counting only the distinct ones).

The product of its digits is 345600, while the sum is 45.

The square root of 66561588 is about 8158.5285438000. The cubic root of 66561588 is about 405.2669844534.

The spelling of 66561588 in words is "sixty-six million, five hundred sixty-one thousand, five hundred eighty-eight".