666111999 has 16 divisors (see below), whose sum is σ = 1042462208. Its totient is φ = 370347552.

The previous prime is 666111997. The next prime is 666112001. The reversal of 666111999 is 999111666.

It is an interprime number because it is at equal distance from previous prime (666111997) and next prime (666112001).

It is not a de Polignac number, because 666111999 - 2¹ = 666111997 is a prime.

666111999 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666111997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 427867 + ... + 429420.

It is an arithmetic number, because the mean of its divisors is an integer number (65153888).

Almost surely, 2^666111999 is an apocalyptic number.

666111999 is a deficient number, since it is larger than the sum of its proper divisors (376350209).

666111999 is a wasteful number, since it uses less digits than its factorization.

666111999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857334.

The product of its digits is 157464, while the sum is 48.

The square root of 666111999 is about 25809.1456464564. The cubic root of 666111999 is about 873.3381240956.

The spelling of 666111999 in words is "six hundred sixty-six million, one hundred eleven thousand, nine hundred ninety-nine".