21806219 has 8 divisors (see below), whose sum is σ = 22706880. Its totient is φ = 20923200.

The previous prime is 21806207. The next prime is 21806227. The reversal of 21806219 is 91260812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21806219 - 2⁸ = 21805963 is a prime.

It is a super-2 number, since 2×21806219² = 951022374151922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21806191 and 21806200.

It is not an unprimeable number, because it can be changed into a prime (21806269) 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 7 ways as a sum of consecutive naturals, for example, 1859 + ... + 6860.

It is an arithmetic number, because the mean of its divisors is an integer number (2838360).

Almost surely, 2^21806219 is an apocalyptic number.

21806219 is a deficient number, since it is larger than the sum of its proper divisors (900661).

21806219 is an equidigital number, since it uses as much as digits as its factorization.

21806219 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8821.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21806219 is about 4669.7129462099. The cubic root of 21806219 is about 279.3788056910.

The spelling of 21806219 in words is "twenty-one million, eight hundred six thousand, two hundred nineteen".