666553666 has 4 divisors (see below), whose sum is σ = 999830502. Its totient is φ = 333276832.

The previous prime is 666553651. The next prime is 666553711. The reversal of 666553666 is 666355666.

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., 647448025 + 19105641 = 25445^2 + 4371^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166638415 + ... + 166638418.

Almost surely, 2^666553666 is an apocalyptic number.

666553666 is a deficient number, since it is larger than the sum of its proper divisors (333276836).

666553666 is a wasteful number, since it uses less digits than its factorization.

666553666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333276835.

The product of its digits is 3499200, while the sum is 49.

The square root of 666553666 is about 25817.7006334801. The cubic root of 666553666 is about 873.5311043599.

The spelling of 666553666 in words is "six hundred sixty-six million, five hundred fifty-three thousand, six hundred sixty-six".