166321381 has 2 divisors, whose sum is σ = 166321382. Its totient is φ = 166321380.

The previous prime is 166321369. The next prime is 166321427. The reversal of 166321381 is 183123661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 140209281 + 26112100 = 11841^2 + 5110^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-166321381 is a prime.

It is a super-2 number, since 2×166321381² = 55325603555494322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166321361) 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 as a sum of consecutive naturals, namely, 83160690 + 83160691.

It is an arithmetic number, because the mean of its divisors is an integer number (83160691).

Almost surely, 2^166321381 is an apocalyptic number.

It is an amenable number.

166321381 is a deficient number, since it is larger than the sum of its proper divisors (1).

166321381 is an equidigital number, since it uses as much as digits as its factorization.

166321381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 31.

The square root of 166321381 is about 12896.5646976239. The cubic root of 166321381 is about 549.9409093542.

The spelling of 166321381 in words is "one hundred sixty-six million, three hundred twenty-one thousand, three hundred eighty-one".