21109191 has 16 divisors (see below), whose sum is σ = 28817376. Its totient is φ = 13741056.

The previous prime is 21109181. The next prime is 21109201. The reversal of 21109191 is 19190112.

It is an interprime number because it is at equal distance from previous prime (21109181) and next prime (21109201).

It is not a de Polignac number, because 21109191 - 2⁵ = 21109159 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21109181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24321 + ... + 25173.

It is an arithmetic number, because the mean of its divisors is an integer number (1801086).

Almost surely, 2^21109191 is an apocalyptic number.

21109191 is a deficient number, since it is larger than the sum of its proper divisors (7708185).

21109191 is a wasteful number, since it uses less digits than its factorization.

21109191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1042.

The product of its (nonzero) digits is 162, while the sum is 24.

The square root of 21109191 is about 4594.4739633608. The cubic root of 21109191 is about 276.3697653678.

It can be divided in two parts, 21 and 109191, that multiplied together give a triangular number (2293011 = T₂₁₄₁).

The spelling of 21109191 in words is "twenty-one million, one hundred nine thousand, one hundred ninety-one".