666520109 has 16 divisors (see below), whose sum is σ = 703261440. Its totient is φ = 630993600.

The previous prime is 666520069. The next prime is 666520117. The reversal of 666520109 is 901025666.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 666520109 - 2¹² = 666516013 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 (666520189) 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, 218972 + ... + 221994.

It is an arithmetic number, because the mean of its divisors is an integer number (43953840).

Almost surely, 2^666520109 is an apocalyptic number.

It is an amenable number.

666520109 is a deficient number, since it is larger than the sum of its proper divisors (36741331).

666520109 is a wasteful number, since it uses less digits than its factorization.

666520109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3220.

The product of its (nonzero) digits is 19440, while the sum is 35.

The square root of 666520109 is about 25817.0507417094. The cubic root of 666520109 is about 873.5164450875.

The spelling of 666520109 in words is "six hundred sixty-six million, five hundred twenty thousand, one hundred nine".