21647449 has 4 divisors (see below), whose sum is σ = 21659364. Its totient is φ = 21635536.

The previous prime is 21647429. The next prime is 21647453. The reversal of 21647449 is 94474612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 16040025 + 5607424 = 4005^2 + 2368^2 .

It is a cyclic number.

It is not a de Polignac number, because 21647449 - 2⁷ = 21647321 is a prime.

It is a super-2 number, since 2×21647449² = 937224096415202, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21647429) 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, 2602 + ... + 7075.

It is an arithmetic number, because the mean of its divisors is an integer number (5414841).

Almost surely, 2^21647449 is an apocalyptic number.

It is an amenable number.

21647449 is a deficient number, since it is larger than the sum of its proper divisors (11915).

21647449 is an equidigital number, since it uses as much as digits as its factorization.

21647449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11914.

The product of its digits is 48384, while the sum is 37.

The square root of 21647449 is about 4652.6819147670. The cubic root of 21647449 is about 278.6991056445.

The spelling of 21647449 in words is "twenty-one million, six hundred forty-seven thousand, four hundred forty-nine".