21361209 has 8 divisors (see below), whose sum is σ = 28503552. Its totient is φ = 14229840.

The previous prime is 21361183. The next prime is 21361217. The reversal of 21361209 is 90216312.

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

It is not a de Polignac number, because 21361209 - 2⁹ = 21360697 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21361229) 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, 4647 + ... + 8019.

It is an arithmetic number, because the mean of its divisors is an integer number (3562944).

Almost surely, 2^21361209 is an apocalyptic number.

It is an amenable number.

21361209 is a deficient number, since it is larger than the sum of its proper divisors (7142343).

21361209 is a wasteful number, since it uses less digits than its factorization.

21361209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5487.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21361209 is about 4621.8187978327. The cubic root of 21361209 is about 277.4652565869.

The spelling of 21361209 in words is "twenty-one million, three hundred sixty-one thousand, two hundred nine".