665642611 has 4 divisors (see below), whose sum is σ = 669726472. Its totient is φ = 661558752.

The previous prime is 665642573. The next prime is 665642647. The reversal of 665642611 is 116246566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 116246566 = 2 ⋅58123283.

It is a cyclic number.

It is not a de Polignac number, because 665642611 - 2²¹ = 663545459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665642671) 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, 2041686 + ... + 2042011.

It is an arithmetic number, because the mean of its divisors is an integer number (167431618).

Almost surely, 2^665642611 is an apocalyptic number.

665642611 is a deficient number, since it is larger than the sum of its proper divisors (4083861).

665642611 is a wasteful number, since it uses less digits than its factorization.

665642611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4083860.

The product of its digits is 51840, while the sum is 37.

The square root of 665642611 is about 25800.0506007256. The cubic root of 665642611 is about 873.1329379993.

The spelling of 665642611 in words is "six hundred sixty-five million, six hundred forty-two thousand, six hundred eleven".