21840055 has 4 divisors (see below), whose sum is σ = 26208072. Its totient is φ = 17472040.

The previous prime is 21840047. The next prime is 21840061. The reversal of 21840055 is 55004812.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21840055 - 2³ = 21840047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2184001 + ... + 2184010.

It is an arithmetic number, because the mean of its divisors is an integer number (6552018).

Almost surely, 2^21840055 is an apocalyptic number.

21840055 is a deficient number, since it is larger than the sum of its proper divisors (4368017).

21840055 is an equidigital number, since it uses as much as digits as its factorization.

21840055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4368016.

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 21840055 is about 4673.3344626722. The cubic root of 21840055 is about 279.5232320149.

Adding to 21840055 its reverse (55004812), we get a palindrome (76844867).

The spelling of 21840055 in words is "twenty-one million, eight hundred forty thousand, fifty-five".