166121021 has 12 divisors (see below), whose sum is σ = 183540000. Its totient is φ = 150238440.

The previous prime is 166121003. The next prime is 166121023. The reversal of 166121021 is 120121661.

It is not a de Polignac number, because 166121021 - 2¹⁰ = 166119997 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 166120984 and 166121002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166121023) 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 11 ways as a sum of consecutive naturals, for example, 20630 + ... + 27528.

It is an arithmetic number, because the mean of its divisors is an integer number (15295000).

Almost surely, 2^166121021 is an apocalyptic number.

166121021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

166121021 is a deficient number, since it is larger than the sum of its proper divisors (17418979).

166121021 is a wasteful number, since it uses less digits than its factorization.

166121021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7120 (or 7109 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 166121021 is about 12888.7943966843. The cubic root of 166121021 is about 549.7199908027.

Adding to 166121021 its reverse (120121661), we get a palindrome (286242682).

The spelling of 166121021 in words is "one hundred sixty-six million, one hundred twenty-one thousand, twenty-one".