209985731 has 2 divisors, whose sum is σ = 209985732. Its totient is φ = 209985730.

The previous prime is 209985691. The next prime is 209985733. The reversal of 209985731 is 137589902.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209985731 is a prime.

It is a super-2 number, since 2×209985731² = 88188014447208722, which contains 22 as substring.

Together with 209985733, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (209985733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104992865 + 104992866.

It is an arithmetic number, because the mean of its divisors is an integer number (104992866).

Almost surely, 2^209985731 is an apocalyptic number.

209985731 is a deficient number, since it is larger than the sum of its proper divisors (1).

209985731 is an equidigital number, since it uses as much as digits as its factorization.

209985731 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 136080, while the sum is 44.

The square root of 209985731 is about 14490.8844105527. The cubic root of 209985731 is about 594.3787324599.

The spelling of 209985731 in words is "two hundred nine million, nine hundred eighty-five thousand, seven hundred thirty-one".