21814209 has 6 divisors (see below), whose sum is σ = 31509426. Its totient is φ = 14542800.

The previous prime is 21814187. The next prime is 21814229. The reversal of 21814209 is 90241812.

It can be written as a sum of positive squares in only one way, i.e., 21762225 + 51984 = 4665^2 + 228^2 .

It is not a de Polignac number, because 21814209 - 2⁹ = 21813697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21814229) 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 5 ways as a sum of consecutive naturals, for example, 1211892 + ... + 1211909.

It is an arithmetic number, because the mean of its divisors is an integer number (5251571).

Almost surely, 2^21814209 is an apocalyptic number.

It is an amenable number.

21814209 is a deficient number, since it is larger than the sum of its proper divisors (9695217).

21814209 is a wasteful number, since it uses less digits than its factorization.

21814209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2423807 (or 2423804 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 21814209 is about 4670.5683808290. The cubic root of 21814209 is about 279.4129238490.

The spelling of 21814209 in words is "twenty-one million, eight hundred fourteen thousand, two hundred nine".