66561012 has 108 divisors (see below), whose sum is σ = 198247140. Its totient is φ = 18772992.

The previous prime is 66561007. The next prime is 66561013. The reversal of 66561012 is 21016566.

It is a happy number.

66561012 is a `hidden beast` number, since 6 + 656 + 1 + 0 + 1 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 22524516 + 44036496 = 4746^2 + 6636^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561013) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 170914 + ... + 171302.

Almost surely, 2^66561012 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 66561012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99123570).

66561012 is an abundant number, since it is smaller than the sum of its proper divisors (131686128).

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

66561012 is a wasteful number, since it uses less digits than its factorization.

66561012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 510 (or 498 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 66561012 is about 8158.4932432404. The cubic root of 66561012 is about 405.2658154386.

Adding to 66561012 its reverse (21016566), we get a palindrome (87577578).

The spelling of 66561012 in words is "sixty-six million, five hundred sixty-one thousand, twelve".