166856639 has 4 divisors (see below), whose sum is σ = 166901880. Its totient is φ = 166811400.

The previous prime is 166856621. The next prime is 166856647. The reversal of 166856639 is 936658661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 936658661 = 6037 ⋅155153.

It is a cyclic number.

It is not a de Polignac number, because 166856639 - 2¹⁶ = 166791103 is a prime.

It is a super-2 number, since 2×166856639² = 55682275956752642, 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 (166856609) 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, 16544 + ... + 24645.

It is an arithmetic number, because the mean of its divisors is an integer number (41725470).

Almost surely, 2^166856639 is an apocalyptic number.

166856639 is a deficient number, since it is larger than the sum of its proper divisors (45241).

166856639 is an equidigital number, since it uses as much as digits as its factorization.

166856639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45240.

The product of its digits is 1399680, while the sum is 50.

The square root of 166856639 is about 12917.2999887747. The cubic root of 166856639 is about 550.5302203641.

The spelling of 166856639 in words is "one hundred sixty-six million, eight hundred fifty-six thousand, six hundred thirty-nine".