66604009 has 4 divisors (see below), whose sum is σ = 67695940. Its totient is φ = 65512080.

The previous prime is 66604003. The next prime is 66604019. The reversal of 66604009 is 90040666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90040666 = 2 ⋅45020333.

It can be written as a sum of positive squares in 2 ways, for example, as 994009 + 65610000 = 997^2 + 8100^2 .

It is a cyclic number.

It is not a de Polignac number, because 66604009 - 2³ = 66604001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66604001) 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, 545874 + ... + 545995.

It is an arithmetic number, because the mean of its divisors is an integer number (16923985).

Almost surely, 2^66604009 is an apocalyptic number.

It is an amenable number.

66604009 is a deficient number, since it is larger than the sum of its proper divisors (1091931).

66604009 is a wasteful number, since it uses less digits than its factorization.

66604009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1091930.

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 66604009 is about 8161.1279244967. The cubic root of 66604009 is about 405.3530610246.

The spelling of 66604009 in words is "sixty-six million, six hundred four thousand, nine".