666516551 has 4 divisors (see below), whose sum is σ = 668195832. Its totient is φ = 664837272.

The previous prime is 666516533. The next prime is 666516553. The reversal of 666516551 is 155615666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155615666 = 2 ⋅77807833.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666516551 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 666516499 and 666516508.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 839045 + ... + 839838.

It is an arithmetic number, because the mean of its divisors is an integer number (167048958).

Almost surely, 2^666516551 is an apocalyptic number.

666516551 is a deficient number, since it is larger than the sum of its proper divisors (1679281).

666516551 is a wasteful number, since it uses less digits than its factorization.

666516551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1679280.

The product of its digits is 162000, while the sum is 41.

The square root of 666516551 is about 25816.9818336691. The cubic root of 666516551 is about 873.5148907573.

The spelling of 666516551 in words is "six hundred sixty-six million, five hundred sixteen thousand, five hundred fifty-one".