21836405 has 8 divisors (see below), whose sum is σ = 26573184. Its totient is φ = 17222800.

The previous prime is 21836323. The next prime is 21836413. The reversal of 21836405 is 50463812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21836405 - 2²⁰ = 20787829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 30401 + ... + 31110.

It is an arithmetic number, because the mean of its divisors is an integer number (3321648).

Almost surely, 2^21836405 is an apocalyptic number.

It is an amenable number.

21836405 is a deficient number, since it is larger than the sum of its proper divisors (4736779).

21836405 is an equidigital number, since it uses as much as digits as its factorization.

21836405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61587.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21836405 is about 4672.9439328971. The cubic root of 21836405 is about 279.5076594558.

The spelling of 21836405 in words is "twenty-one million, eight hundred thirty-six thousand, four hundred five".