221891909 has 2 divisors, whose sum is σ = 221891910. Its totient is φ = 221891908.

The previous prime is 221891897. The next prime is 221891941. The reversal of 221891909 is 909198122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 216237025 + 5654884 = 14705^2 + 2378^2 .

It is a cyclic number.

It is not a de Polignac number, because 221891909 - 2²⁰ = 220843333 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221891809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110945954 + 110945955.

It is an arithmetic number, because the mean of its divisors is an integer number (110945955).

Almost surely, 2^221891909 is an apocalyptic number.

It is an amenable number.

221891909 is a deficient number, since it is larger than the sum of its proper divisors (1).

221891909 is an equidigital number, since it uses as much as digits as its factorization.

221891909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 221891909 is about 14896.0366876562. The cubic root of 221891909 is about 605.4066059802.

The spelling of 221891909 in words is "two hundred twenty-one million, eight hundred ninety-one thousand, nine hundred nine".