21084191 has 4 divisors (see below), whose sum is σ = 21654072. Its totient is φ = 20514312.

The previous prime is 21084187. The next prime is 21084227. The reversal of 21084191 is 19148012.

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 21084191 - 2² = 21084187 is a prime.

It is a super-2 number, since 2×21084191² = 889086220248962, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21084191.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21084691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 284885 + ... + 284958.

It is an arithmetic number, because the mean of its divisors is an integer number (5413518).

Almost surely, 2^21084191 is an apocalyptic number.

21084191 is a deficient number, since it is larger than the sum of its proper divisors (569881).

21084191 is an equidigital number, since it uses as much as digits as its factorization.

21084191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 569880.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 21084191 is about 4591.7524976854. The cubic root of 21084191 is about 276.2606190167.

The spelling of 21084191 in words is "twenty-one million, eighty-four thousand, one hundred ninety-one".