66651609 has 16 divisors (see below), whose sum is σ = 91937664. Its totient is φ = 42921600.

The previous prime is 66651583. The next prime is 66651619. The reversal of 66651609 is 90615666.

It is not a de Polignac number, because 66651609 - 2¹⁷ = 66520537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66651619) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10039 + ... + 15299.

It is an arithmetic number, because the mean of its divisors is an integer number (5746104).

Almost surely, 2^66651609 is an apocalyptic number.

It is an amenable number.

66651609 is a deficient number, since it is larger than the sum of its proper divisors (25286055).

66651609 is a wasteful number, since it uses less digits than its factorization.

66651609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5408.

The product of its (nonzero) digits is 58320, while the sum is 39.

The square root of 66651609 is about 8164.0436672032. The cubic root of 66651609 is about 405.4496028161.

The spelling of 66651609 in words is "sixty-six million, six hundred fifty-one thousand, six hundred nine".