666749815 has 4 divisors (see below), whose sum is σ = 800099784. Its totient is φ = 533399848.

The previous prime is 666749813. The next prime is 666749851. The reversal of 666749815 is 518947666.

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 666749815 - 2¹ = 666749813 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 (666749813) 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, 66674977 + ... + 66674986.

It is an arithmetic number, because the mean of its divisors is an integer number (200024946).

Almost surely, 2^666749815 is an apocalyptic number.

666749815 is a deficient number, since it is larger than the sum of its proper divisors (133349969).

666749815 is a wasteful number, since it uses less digits than its factorization.

666749815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133349968.

The product of its digits is 2177280, while the sum is 52.

The square root of 666749815 is about 25821.4990850648. The cubic root of 666749815 is about 873.6167816063.

The spelling of 666749815 in words is "six hundred sixty-six million, seven hundred forty-nine thousand, eight hundred fifteen".