66516517 has 4 divisors (see below), whose sum is σ = 68810220. Its totient is φ = 64222816.

The previous prime is 66516509. The next prime is 66516521. The reversal of 66516517 is 71561566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71561566 = 2 ⋅35780783.

It can be written as a sum of positive squares in 2 ways, for example, as 38118276 + 28398241 = 6174^2 + 5329^2 .

It is a cyclic number.

It is not a de Polignac number, because 66516517 - 2³ = 66516509 is a prime.

It is a super-2 number, since 2×66516517² = 8848894067622578, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66516547) 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, 1146808 + ... + 1146865.

It is an arithmetic number, because the mean of its divisors is an integer number (17202555).

Almost surely, 2^66516517 is an apocalyptic number.

It is an amenable number.

66516517 is a deficient number, since it is larger than the sum of its proper divisors (2293703).

66516517 is a wasteful number, since it uses less digits than its factorization.

66516517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2293702.

The product of its digits is 37800, while the sum is 37.

The square root of 66516517 is about 8155.7658745209. The cubic root of 66516517 is about 405.1754906798.

The spelling of 66516517 in words is "sixty-six million, five hundred sixteen thousand, five hundred seventeen".