213009991 has 4 divisors (see below), whose sum is σ = 215706400. Its totient is φ = 210313584.

The previous prime is 213009989. The next prime is 213010013. The reversal of 213009991 is 199900312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 213009991 - 2¹ = 213009989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (213009911) 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 in 3 ways as a sum of consecutive naturals, for example, 1348086 + ... + 1348243.

It is an arithmetic number, because the mean of its divisors is an integer number (53926600).

Almost surely, 2^213009991 is an apocalyptic number.

213009991 is a deficient number, since it is larger than the sum of its proper divisors (2696409).

213009991 is an equidigital number, since it uses as much as digits as its factorization.

213009991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2696408.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 213009991 is about 14594.8618013327. The cubic root of 213009991 is about 597.2185994231.

The spelling of 213009991 in words is "two hundred thirteen million, nine thousand, nine hundred ninety-one".