66565997 has 4 divisors (see below), whose sum is σ = 68365116. Its totient is φ = 64766880.

The previous prime is 66565981. The next prime is 66566011. The reversal of 66565997 is 79956566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79956566 = 2 ⋅39978283.

It can be written as a sum of positive squares in 2 ways, for example, as 63696361 + 2869636 = 7981^2 + 1694^2 .

It is a cyclic number.

It is not a de Polignac number, because 66565997 - 2⁴ = 66565981 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 (66565957) 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, 899504 + ... + 899577.

It is an arithmetic number, because the mean of its divisors is an integer number (17091279).

Almost surely, 2^66565997 is an apocalyptic number.

It is an amenable number.

66565997 is a deficient number, since it is larger than the sum of its proper divisors (1799119).

66565997 is a wasteful number, since it uses less digits than its factorization.

66565997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1799118.

The product of its digits is 3061800, while the sum is 53.

The square root of 66565997 is about 8158.7987473647. The cubic root of 66565997 is about 405.2759324705.

The spelling of 66565997 in words is "sixty-six million, five hundred sixty-five thousand, nine hundred ninety-seven".