66706661 has 4 divisors (see below), whose sum is σ = 76236192. Its totient is φ = 57177132.

The previous prime is 66706643. The next prime is 66706667. The reversal of 66706661 is 16660766.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16660766 = 2 ⋅8330383.

It is a cyclic number.

It is not a de Polignac number, because 66706661 - 2²² = 62512357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66706667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4764755 + ... + 4764768.

It is an arithmetic number, because the mean of its divisors is an integer number (19059048).

Almost surely, 2^66706661 is an apocalyptic number.

It is an amenable number.

66706661 is a deficient number, since it is larger than the sum of its proper divisors (9529531).

66706661 is an equidigital number, since it uses as much as digits as its factorization.

66706661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9529530.

The product of its (nonzero) digits is 54432, while the sum is 38.

The square root of 66706661 is about 8167.4145847998. The cubic root of 66706661 is about 405.5612013670.

It can be divided in two parts, 6670 and 6661, that added together give a palindrome (13331).

The spelling of 66706661 in words is "sixty-six million, seven hundred six thousand, six hundred sixty-one".