21505383 has 12 divisors (see below), whose sum is σ = 31438680. Its totient is φ = 14163696.

The previous prime is 21505381. The next prime is 21505417. The reversal of 21505383 is 38350512.

It is not a de Polignac number, because 21505383 - 2¹ = 21505381 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505381) 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 11 ways as a sum of consecutive naturals, for example, 13648 + ... + 15141.

It is an arithmetic number, because the mean of its divisors is an integer number (2619890).

Almost surely, 2^21505383 is an apocalyptic number.

21505383 is a deficient number, since it is larger than the sum of its proper divisors (9933297).

21505383 is a wasteful number, since it uses less digits than its factorization.

21505383 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28878 (or 28875 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21505383 is about 4637.3896752376. The cubic root of 21505383 is about 278.0880929523.

Adding to 21505383 its reverse (38350512), we get a palindrome (59855895).

The spelling of 21505383 in words is "twenty-one million, five hundred five thousand, three hundred eighty-three".