66501661 has 4 divisors (see below), whose sum is σ = 66599712. Its totient is φ = 66403612.

The previous prime is 66501649. The next prime is 66501679. The reversal of 66501661 is 16610566.

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.

It is a cyclic number.

It is not a de Polignac number, because 66501661 - 2⁵ = 66501629 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 (66505661) 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 3 ways as a sum of consecutive naturals, for example, 48001 + ... + 49366.

It is an arithmetic number, because the mean of its divisors is an integer number (16649928).

Almost surely, 2^66501661 is an apocalyptic number.

It is an amenable number.

66501661 is a deficient number, since it is larger than the sum of its proper divisors (98051).

66501661 is an equidigital number, since it uses as much as digits as its factorization.

66501661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98050.

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

The square root of 66501661 is about 8154.8550569584. The cubic root of 66501661 is about 405.1453240609.

The spelling of 66501661 in words is "sixty-six million, five hundred one thousand, six hundred sixty-one".