21682209 has 4 divisors (see below), whose sum is σ = 28909616. Its totient is φ = 14454804.

The previous prime is 21682201. The next prime is 21682223. The reversal of 21682209 is 90228612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21682209 - 2³ = 21682201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21682201) 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, 3613699 + ... + 3613704.

It is an arithmetic number, because the mean of its divisors is an integer number (7227404).

Almost surely, 2^21682209 is an apocalyptic number.

It is an amenable number.

21682209 is a deficient number, since it is larger than the sum of its proper divisors (7227407).

21682209 is an equidigital number, since it uses as much as digits as its factorization.

21682209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7227406.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21682209 is about 4656.4158963735. The cubic root of 21682209 is about 278.8481978896.

The spelling of 21682209 in words is "twenty-one million, six hundred eighty-two thousand, two hundred nine".