21648109 has 4 divisors (see below), whose sum is σ = 24740704. Its totient is φ = 18555516.

The previous prime is 21648079. The next prime is 21648127. The reversal of 21648109 is 90184612.

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 21648109 - 2⁹ = 21647597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21648139) 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 3 ways as a sum of consecutive naturals, for example, 1546287 + ... + 1546300.

It is an arithmetic number, because the mean of its divisors is an integer number (6185176).

Almost surely, 2^21648109 is an apocalyptic number.

It is an amenable number.

21648109 is a deficient number, since it is larger than the sum of its proper divisors (3092595).

21648109 is an equidigital number, since it uses as much as digits as its factorization.

21648109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3092594.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21648109 is about 4652.7528410609. The cubic root of 21648109 is about 278.7019379958.

The spelling of 21648109 in words is "twenty-one million, six hundred forty-eight thousand, one hundred nine".