209213881 has 2 divisors, whose sum is σ = 209213882. Its totient is φ = 209213880.

The previous prime is 209213863. The next prime is 209213887. The reversal of 209213881 is 188312902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 114832656 + 94381225 = 10716^2 + 9715^2 .

It is a cyclic number.

It is not a de Polignac number, because 209213881 - 2²⁷ = 74996153 is a prime.

It is a super-2 number, since 2×209213881² = 87540896006164322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (209213887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104606940 + 104606941.

It is an arithmetic number, because the mean of its divisors is an integer number (104606941).

Almost surely, 2^209213881 is an apocalyptic number.

It is an amenable number.

209213881 is a deficient number, since it is larger than the sum of its proper divisors (1).

209213881 is an equidigital number, since it uses as much as digits as its factorization.

209213881 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 209213881 is about 14464.2276323349. The cubic root of 209213881 is about 593.6495805648.

The spelling of 209213881 in words is "two hundred nine million, two hundred thirteen thousand, eight hundred eighty-one".