166121261 has 2 divisors, whose sum is σ = 166121262. Its totient is φ = 166121260.

The previous prime is 166121243. The next prime is 166121321. The reversal of 166121261 is 162121661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 97397161 + 68724100 = 9869^2 + 8290^2 .

It is a cyclic number.

It is not a de Polignac number, because 166121261 - 2²² = 161926957 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 166121261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166121561) 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, 83060630 + 83060631.

It is an arithmetic number, because the mean of its divisors is an integer number (83060631).

Almost surely, 2^166121261 is an apocalyptic number.

It is an amenable number.

166121261 is a deficient number, since it is larger than the sum of its proper divisors (1).

166121261 is an equidigital number, since it uses as much as digits as its factorization.

166121261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 26.

The square root of 166121261 is about 12888.8037070940. The cubic root of 166121261 is about 549.7202555349.

It can be divided in two parts, 1661 and 21261, that added together give a palindrome (22922).

The spelling of 166121261 in words is "one hundred sixty-six million, one hundred twenty-one thousand, two hundred sixty-one".