166121281 has 4 divisors (see below), whose sum is σ = 171480064. Its totient is φ = 160762500.

The previous prime is 166121261. The next prime is 166121321. The reversal of 166121281 is 182121661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 182121661 = 61 ⋅2985601.

It is a cyclic number.

It is not a de Polignac number, because 166121281 - 2¹⁵ = 166088513 is a prime.

It is a super-2 number, since 2×166121281² = 55192560002161922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166121261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2679345 + ... + 2679406.

It is an arithmetic number, because the mean of its divisors is an integer number (42870016).

Almost surely, 2^166121281 is an apocalyptic number.

It is an amenable number.

166121281 is a deficient number, since it is larger than the sum of its proper divisors (5358783).

166121281 is an equidigital number, since it uses as much as digits as its factorization.

166121281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5358782.

The product of its digits is 1152, while the sum is 28.

The square root of 166121281 is about 12888.8044829612. The cubic root of 166121281 is about 549.7202775959.

The spelling of 166121281 in words is "one hundred sixty-six million, one hundred twenty-one thousand, two hundred eighty-one".