209888991 has 48 divisors (see below), whose sum is σ = 345945600. Its totient is φ = 121559616.

The previous prime is 209888969. The next prime is 209889011. The reversal of 209888991 is 199888902.

It is a happy number.

It is not a de Polignac number, because 209888991 - 2⁶ = 209888927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209888911) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 584470 + ... + 584828.

It is an arithmetic number, because the mean of its divisors is an integer number (7207200).

Almost surely, 2^209888991 is an apocalyptic number.

209888991 is a deficient number, since it is larger than the sum of its proper divisors (136056609).

209888991 is a wasteful number, since it uses less digits than its factorization.

209888991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 660 (or 657 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 54.

The square root of 209888991 is about 14487.5460655005. The cubic root of 209888991 is about 594.2874420809.

The spelling of 209888991 in words is "two hundred nine million, eight hundred eighty-eight thousand, nine hundred ninety-one".