66561000 has 128 divisors (see below), whose sum is σ = 226661760. Its totient is φ = 16128000.

The previous prime is 66560987. The next prime is 66561007. The reversal of 66561000 is 16566.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is not an unprimeable number, because it can be changed into a prime (66561007) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 31992 + ... + 34008.

It is an arithmetic number, because the mean of its divisors is an integer number (1770795).

Almost surely, 2^66561000 is an apocalyptic number.

66561000 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 66561000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113330880).

66561000 is an abundant number, since it is smaller than the sum of its proper divisors (160100760).

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

66561000 is a wasteful number, since it uses less digits than its factorization.

66561000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2052 (or 2038 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 66561000 is about 8158.4925078105. The cubic root of 66561000 is about 405.2657910840.

Adding to 66561000 its reverse (16566), we get a palindrome (66577566).

The spelling of 66561000 in words is "sixty-six million, five hundred sixty-one thousand".