209661253 has 2 divisors, whose sum is σ = 209661254. Its totient is φ = 209661252.

The previous prime is 209661251. The next prime is 209661259. The reversal of 209661253 is 352166902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 206726884 + 2934369 = 14378^2 + 1713^2 .

It is a cyclic number.

It is not a de Polignac number, because 209661253 - 2¹ = 209661251 is a prime.

Together with 209661251, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209661251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104830626 + 104830627.

It is an arithmetic number, because the mean of its divisors is an integer number (104830627).

Almost surely, 2^209661253 is an apocalyptic number.

It is an amenable number.

209661253 is a deficient number, since it is larger than the sum of its proper divisors (1).

209661253 is an equidigital number, since it uses as much as digits as its factorization.

209661253 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 34.

The square root of 209661253 is about 14479.6841471076. The cubic root of 209661253 is about 594.0724223653.

The spelling of 209661253 in words is "two hundred nine million, six hundred sixty-one thousand, two hundred fifty-three".