209122421 has 2 divisors, whose sum is σ = 209122422. Its totient is φ = 209122420.

The previous prime is 209122399. The next prime is 209122429. The reversal of 209122421 is 124221902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 194909521 + 14212900 = 13961^2 + 3770^2 .

It is a cyclic number.

It is not a de Polignac number, because 209122421 - 2⁶ = 209122357 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209122429) 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, 104561210 + 104561211.

It is an arithmetic number, because the mean of its divisors is an integer number (104561211).

Almost surely, 2^209122421 is an apocalyptic number.

It is an amenable number.

209122421 is a deficient number, since it is larger than the sum of its proper divisors (1).

209122421 is an equidigital number, since it uses as much as digits as its factorization.

209122421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 209122421 is about 14461.0656937862. The cubic root of 209122421 is about 593.5630612826.

The spelling of 209122421 in words is "two hundred nine million, one hundred twenty-two thousand, four hundred twenty-one".