210991423 has 4 divisors (see below), whose sum is σ = 211022560. Its totient is φ = 210960288.

The previous prime is 210991421. The next prime is 210991433. The reversal of 210991423 is 324199012.

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 210991423 - 2¹ = 210991421 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 (210991421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 618 + ... + 20551.

It is an arithmetic number, because the mean of its divisors is an integer number (52755640).

Almost surely, 2^210991423 is an apocalyptic number.

210991423 is a deficient number, since it is larger than the sum of its proper divisors (31137).

210991423 is an equidigital number, since it uses as much as digits as its factorization.

210991423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31136.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 210991423 is about 14525.5438108182. The cubic root of 210991423 is about 595.3261145675.

It can be divided in two parts, 21099 and 1423, that added together give a palindrome (22522).

The spelling of 210991423 in words is "two hundred ten million, nine hundred ninety-one thousand, four hundred twenty-three".