21840205 has 8 divisors (see below), whose sum is σ = 26524512. Its totient is φ = 17261328.

The previous prime is 21840199. The next prime is 21840209. The reversal of 21840205 is 50204812.

21840205 = T₉₄ + T₉₅ + ... + T₅₀₈.

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

It is a cyclic number.

It is not a de Polignac number, because 21840205 - 2³ = 21840197 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 (21840209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25899 + ... + 26728.

It is an arithmetic number, because the mean of its divisors is an integer number (3315564).

Almost surely, 2^21840205 is an apocalyptic number.

It is an amenable number.

21840205 is a deficient number, since it is larger than the sum of its proper divisors (4684307).

21840205 is an equidigital number, since it uses as much as digits as its factorization.

21840205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52715.

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 21840205 is about 4673.3505111429. The cubic root of 21840205 is about 279.5238719459.

The spelling of 21840205 in words is "twenty-one million, eight hundred forty thousand, two hundred five".