66706909 has 4 divisors (see below), whose sum is σ = 66746716. Its totient is φ = 66667104.

The previous prime is 66706879. The next prime is 66706943. The reversal of 66706909 is 90960766.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11902500 + 54804409 = 3450^2 + 7403^2 .

It is a cyclic number.

It is not a de Polignac number, because 66706909 - 2¹⁷ = 66575837 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 (66706949) 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, 17274 + ... + 20779.

It is an arithmetic number, because the mean of its divisors is an integer number (16686679).

Almost surely, 2^66706909 is an apocalyptic number.

It is an amenable number.

66706909 is a deficient number, since it is larger than the sum of its proper divisors (39807).

66706909 is a wasteful number, since it uses less digits than its factorization.

66706909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39806.

The product of its (nonzero) digits is 122472, while the sum is 43.

The square root of 66706909 is about 8167.4297670687. The cubic root of 66706909 is about 405.5617039608.

The spelling of 66706909 in words is "sixty-six million, seven hundred six thousand, nine hundred nine".