666389506 has 4 divisors (see below), whose sum is σ = 999584262. Its totient is φ = 333194752.

The previous prime is 666389501. The next prime is 666389543. The reversal of 666389506 is 605983666.

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

It can be written as a sum of positive squares in only one way, i.e., 465912225 + 200477281 = 21585^2 + 14159^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 666389506.

It is not an unprimeable number, because it can be changed into a prime (666389501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166597375 + ... + 166597378.

Almost surely, 2^666389506 is an apocalyptic number.

666389506 is a deficient number, since it is larger than the sum of its proper divisors (333194756).

666389506 is a wasteful number, since it uses less digits than its factorization.

666389506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333194755.

The product of its (nonzero) digits is 1399680, while the sum is 49.

The square root of 666389506 is about 25814.5212235284. The cubic root of 666389506 is about 873.4593868837.

It can be divided in two parts, 6663 and 89506, that added together give a palindrome (96169).

The spelling of 666389506 in words is "six hundred sixty-six million, three hundred eighty-nine thousand, five hundred six".