21609449 has 4 divisors (see below), whose sum is σ = 22306560. Its totient is φ = 20912340.

The previous prime is 21609439. The next prime is 21609461. The reversal of 21609449 is 94490612.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21609449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21609439) 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, 348509 + ... + 348570.

It is an arithmetic number, because the mean of its divisors is an integer number (5576640).

Almost surely, 2^21609449 is an apocalyptic number.

It is an amenable number.

21609449 is a deficient number, since it is larger than the sum of its proper divisors (697111).

21609449 is an equidigital number, since it uses as much as digits as its factorization.

21609449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 697110.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21609449 is about 4648.5964548453. The cubic root of 21609449 is about 278.5359337011.

The spelling of 21609449 in words is "twenty-one million, six hundred nine thousand, four hundred forty-nine".