166117381 has 2 divisors, whose sum is σ = 166117382. Its totient is φ = 166117380.

The previous prime is 166117379. The next prime is 166117403. The reversal of 166117381 is 183711661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 140209281 + 25908100 = 11841^2 + 5090^2 .

It is a cyclic number.

It is not a de Polignac number, because 166117381 - 2¹ = 166117379 is a prime.

It is a super-2 number, since 2×166117381² = 55189968540598322, which contains 22 as substring.

Together with 166117379, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166117331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83058690 + 83058691.

It is an arithmetic number, because the mean of its divisors is an integer number (83058691).

Almost surely, 2^166117381 is an apocalyptic number.

166117381 is the 8152-nd centered pentagonal number.

It is an amenable number.

166117381 is a deficient number, since it is larger than the sum of its proper divisors (1).

166117381 is an equidigital number, since it uses as much as digits as its factorization.

166117381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 34.

The square root of 166117381 is about 12888.6531879790. The cubic root of 166117381 is about 549.7159756669.

The spelling of 166117381 in words is "one hundred sixty-six million, one hundred seventeen thousand, three hundred eighty-one".