66510661 has 4 divisors (see below), whose sum is σ = 76012192. Its totient is φ = 57009132.

The previous prime is 66510649. The next prime is 66510677. The reversal of 66510661 is 16601566.

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: 16601566 = 2 ⋅8300783.

It is a cyclic number.

It is not a de Polignac number, because 66510661 - 2⁷ = 66510533 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 (66510611) 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, 4750755 + ... + 4750768.

It is an arithmetic number, because the mean of its divisors is an integer number (19003048).

Almost surely, 2^66510661 is an apocalyptic number.

It is an amenable number.

66510661 is a deficient number, since it is larger than the sum of its proper divisors (9501531).

66510661 is an equidigital number, since it uses as much as digits as its factorization.

66510661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9501530.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 66510661 is about 8155.4068568037. The cubic root of 66510661 is about 405.1636000126.

The spelling of 66510661 in words is "sixty-six million, five hundred ten thousand, six hundred sixty-one".