201997909 has 2 divisors, whose sum is σ = 201997910. Its totient is φ = 201997908.

The previous prime is 201997907. The next prime is 201997931. The reversal of 201997909 is 909799102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 140422500 + 61575409 = 11850^2 + 7847^2 .

It is a cyclic number.

It is not a de Polignac number, because 201997909 - 2¹ = 201997907 is a prime.

Together with 201997907, 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 (201997907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 100998954 + 100998955.

It is an arithmetic number, because the mean of its divisors is an integer number (100998955).

Almost surely, 2^201997909 is an apocalyptic number.

It is an amenable number.

201997909 is a deficient number, since it is larger than the sum of its proper divisors (1).

201997909 is an equidigital number, since it uses as much as digits as its factorization.

201997909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 91854, while the sum is 46.

The square root of 201997909 is about 14212.5968422382. The cubic root of 201997909 is about 586.7444062716.

The spelling of 201997909 in words is "two hundred one million, nine hundred ninety-seven thousand, nine hundred nine".