21043655 has 4 divisors (see below), whose sum is σ = 25252392. Its totient is φ = 16834920.

The previous prime is 21043613. The next prime is 21043661. The reversal of 21043655 is 55634012.

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

It is not a de Polignac number, because 21043655 - 2⁶ = 21043591 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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2104361 + ... + 2104370.

It is an arithmetic number, because the mean of its divisors is an integer number (6313098).

Almost surely, 2^21043655 is an apocalyptic number.

21043655 is a deficient number, since it is larger than the sum of its proper divisors (4208737).

21043655 is an equidigital number, since it uses as much as digits as its factorization.

21043655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4208736.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21043655 is about 4587.3363731037. The cubic root of 21043655 is about 276.0834612466.

Adding to 21043655 its reverse (55634012), we get a palindrome (76677667).

The spelling of 21043655 in words is "twenty-one million, forty-three thousand, six hundred fifty-five".