21796809 has 4 divisors (see below), whose sum is σ = 29062416. Its totient is φ = 14531204.

The previous prime is 21796807. The next prime is 21796843. The reversal of 21796809 is 90869712.

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 not a de Polignac number, because 21796809 - 2¹ = 21796807 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21796807) 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, 3632799 + ... + 3632804.

It is an arithmetic number, because the mean of its divisors is an integer number (7265604).

Almost surely, 2^21796809 is an apocalyptic number.

It is an amenable number.

21796809 is a deficient number, since it is larger than the sum of its proper divisors (7265607).

21796809 is an equidigital number, since it uses as much as digits as its factorization.

21796809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7265606.

The product of its (nonzero) digits is 54432, while the sum is 42.

The square root of 21796809 is about 4668.7052809103. The cubic root of 21796809 is about 279.3386132913.

The spelling of 21796809 in words is "twenty-one million, seven hundred ninety-six thousand, eight hundred nine".