666516555 has 24 divisors (see below), whose sum is σ = 1182166128. Its totient is φ = 347207616.

The previous prime is 666516553. The next prime is 666516577. The reversal of 666516555 is 555615666.

It is not a de Polignac number, because 666516555 - 2¹ = 666516553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 666516555.

It is not an unprimeable number, because it can be changed into a prime (666516553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 170292 + ... + 174161.

It is an arithmetic number, because the mean of its divisors is an integer number (49256922).

Almost surely, 2^666516555 is an apocalyptic number.

666516555 is a deficient number, since it is larger than the sum of its proper divisors (515649573).

666516555 is a wasteful number, since it uses less digits than its factorization.

666516555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 344507 (or 344504 counting only the distinct ones).

The product of its digits is 810000, while the sum is 45.

The square root of 666516555 is about 25816.9819111375. The cubic root of 666516555 is about 873.5148925047.

It can be divided in two parts, 6665 and 16555, that added together give a triangular number (23220 = T₂₁₅).

The spelling of 666516555 in words is "six hundred sixty-six million, five hundred sixteen thousand, five hundred fifty-five".