21305055 has 16 divisors (see below), whose sum is σ = 34205184. Its totient is φ = 11323680.

The previous prime is 21305047. The next prime is 21305059. The reversal of 21305055 is 55050312.

It is not a de Polignac number, because 21305055 - 2³ = 21305047 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305059) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2382 + ... + 6948.

It is an arithmetic number, because the mean of its divisors is an integer number (2137824).

Almost surely, 2^21305055 is an apocalyptic number.

21305055 is a deficient number, since it is larger than the sum of its proper divisors (12900129).

21305055 is a wasteful number, since it uses less digits than its factorization.

21305055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4886.

The product of its (nonzero) digits is 750, while the sum is 21.

The square root of 21305055 is about 4615.7399190162. The cubic root of 21305055 is about 277.2219111715.

Adding to 21305055 its reverse (55050312), we get a palindrome (76355367).

The spelling of 21305055 in words is "twenty-one million, three hundred five thousand, fifty-five".