20161666433221 has 2 divisors, whose sum is σ = 20161666433222. Its totient is φ = 20161666433220.

The previous prime is 20161666433213. The next prime is 20161666433243. The reversal of 20161666433221 is 12233466616102.

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., 17740826064196 + 2420840369025 = 4211986^2 + 1555905^2 .

It is a cyclic number.

It is not a de Polignac number, because 20161666433221 - 2³ = 20161666433213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20161666433291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10080833216610 + 10080833216611.

It is an arithmetic number, because the mean of its divisors is an integer number (10080833216611).

Almost surely, 2^{20161666433221} is an apocalyptic number.

It is an amenable number.

20161666433221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20161666433221 is an equidigital number, since it uses as much as digits as its factorization.

20161666433221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 373248, while the sum is 43.

The spelling of 20161666433221 in words is "twenty trillion, one hundred sixty-one billion, six hundred sixty-six million, four hundred thirty-three thousand, two hundred twenty-one".