16921209 has 4 divisors (see below), whose sum is σ = 22561616. Its totient is φ = 11280804.

The previous prime is 16921187. The next prime is 16921279. The reversal of 16921209 is 90212961.

It is a happy number.

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 16921209 - 2¹² = 16917113 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (16921279) 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, 2820199 + ... + 2820204.

It is an arithmetic number, because the mean of its divisors is an integer number (5640404).

Almost surely, 2^16921209 is an apocalyptic number.

It is an amenable number.

16921209 is a deficient number, since it is larger than the sum of its proper divisors (5640407).

16921209 is an equidigital number, since it uses as much as digits as its factorization.

16921209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5640406.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 16921209 is about 4113.5397165945. The cubic root of 16921209 is about 256.7303009328.

The spelling of 16921209 in words is "sixteen million, nine hundred twenty-one thousand, two hundred nine".