666355639 has 4 divisors (see below), whose sum is σ = 666725400. Its totient is φ = 665985880.

The previous prime is 666355637. The next prime is 666355673. The reversal of 666355639 is 936553666.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 666355639 - 2¹ = 666355637 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 666355592 and 666355601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666355637) 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, 182164 + ... + 185785.

It is an arithmetic number, because the mean of its divisors is an integer number (166681350).

Almost surely, 2^666355639 is an apocalyptic number.

666355639 is a deficient number, since it is larger than the sum of its proper divisors (369761).

666355639 is a wasteful number, since it uses less digits than its factorization.

666355639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369760.

The product of its digits is 2624400, while the sum is 49.

The square root of 666355639 is about 25813.8652471884. The cubic root of 666355639 is about 873.4445897569. Note that the first 3 decimals are identical.

The spelling of 666355639 in words is "six hundred sixty-six million, three hundred fifty-five thousand, six hundred thirty-nine".