21153243 has 16 divisors (see below), whose sum is σ = 29223936. Its totient is φ = 13601280.

The previous prime is 21153227. The next prime is 21153257. The reversal of 21153243 is 34235112.

It is not a de Polignac number, because 21153243 - 2⁴ = 21153227 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21153263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8955 + ... + 11067.

It is an arithmetic number, because the mean of its divisors is an integer number (1826496).

Almost surely, 2^21153243 is an apocalyptic number.

21153243 is a deficient number, since it is larger than the sum of its proper divisors (8070693).

21153243 is a wasteful number, since it uses less digits than its factorization.

21153243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2234.

The product of its digits is 720, while the sum is 21.

The square root of 21153243 is about 4599.2654848356. The cubic root of 21153243 is about 276.5618804480.

Adding to 21153243 its reverse (34235112), we get a palindrome (55388355).

It can be divided in two parts, 211532 and 43, that added together give a triangular number (211575 = T₆₅₀).

The spelling of 21153243 in words is "twenty-one million, one hundred fifty-three thousand, two hundred forty-three".