166021 has 2 divisors, whose sum is σ = 166022. Its totient is φ = 166020.

The previous prime is 166013. The next prime is 166027. The reversal of 166021 is 120661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 108900 + 57121 = 330^2 + 239^2 .

It is an emirp because it is prime and its reverse (120661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 166021 - 2³ = 166013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 165986 and 166004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83010 + 83011.

It is an arithmetic number, because the mean of its divisors is an integer number (83011).

2¹⁶⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

166021 is a deficient number, since it is larger than the sum of its proper divisors (1).

166021 is an equidigital number, since it uses as much as digits as its factorization.

166021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 166021 is about 407.4567461707. The cubic root of 166021 is about 54.9609640365.

Adding to 166021 its reverse (120661), we get a palindrome (286682).

It can be divided in two parts, 1660 and 21, that added together give a square (1681 = 41²).

The spelling of 166021 in words is "one hundred sixty-six thousand, twenty-one".