666538 has 4 divisors (see below), whose sum is σ = 999810. Its totient is φ = 333268.

The previous prime is 666529. The next prime is 666541. The reversal of 666538 is 835666.

666538 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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., 635209 + 31329 = 797^2 + 177^2 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666538.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166633 + ... + 166636.

2⁶⁶⁶⁵³⁸ is an apocalyptic number.

666538 is a deficient number, since it is larger than the sum of its proper divisors (333272).

666538 is a wasteful number, since it uses less digits than its factorization.

666538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333271.

The product of its digits is 25920, while the sum is 34.

The square root of 666538 is about 816.4177852056. The cubic root of 666538 is about 87.3524260777.

The spelling of 666538 in words is "six hundred sixty-six thousand, five hundred thirty-eight".