21849409 has 4 divisors (see below), whose sum is σ = 22261716. Its totient is φ = 21437104.

The previous prime is 21849361. The next prime is 21849413. The reversal of 21849409 is 90494812.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9090225 + 12759184 = 3015^2 + 3572^2 .

It is a cyclic number.

It is not a de Polignac number, because 21849409 - 2¹¹ = 21847361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21849419) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 206074 + ... + 206179.

It is an arithmetic number, because the mean of its divisors is an integer number (5565429).

Almost surely, 2^21849409 is an apocalyptic number.

It is an amenable number.

21849409 is a deficient number, since it is larger than the sum of its proper divisors (412307).

21849409 is an equidigital number, since it uses as much as digits as its factorization.

21849409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 412306.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21849409 is about 4674.3351398889. The cubic root of 21849409 is about 279.5631325114.

The spelling of 21849409 in words is "twenty-one million, eight hundred forty-nine thousand, four hundred nine".