221666129 has 2 divisors, whose sum is σ = 221666130. Its totient is φ = 221666128.

The previous prime is 221666119. The next prime is 221666143. The reversal of 221666129 is 921666122.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 214563904 + 7102225 = 14648^2 + 2665^2 .

It is a cyclic number.

It is not a de Polignac number, because 221666129 - 2⁴ = 221666113 is a prime.

It is not a weakly prime, because it can be changed into another prime (221666119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110833064 + 110833065.

It is an arithmetic number, because the mean of its divisors is an integer number (110833065).

Almost surely, 2^221666129 is an apocalyptic number.

It is an amenable number.

221666129 is a deficient number, since it is larger than the sum of its proper divisors (1).

221666129 is an equidigital number, since it uses as much as digits as its factorization.

221666129 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 35.

The square root of 221666129 is about 14888.4562329343. The cubic root of 221666129 is about 605.2011980233.

The spelling of 221666129 in words is "two hundred twenty-one million, six hundred sixty-six thousand, one hundred twenty-nine".