21220243 has 4 divisors (see below), whose sum is σ = 23149368. Its totient is φ = 19291120.

The previous prime is 21220231. The next prime is 21220261. The reversal of 21220243 is 34202212.

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

It is a cyclic number.

It is not a de Polignac number, because 21220243 - 2⁵ = 21220211 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21220223) 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 3 ways as a sum of consecutive naturals, for example, 964546 + ... + 964567.

It is an arithmetic number, because the mean of its divisors is an integer number (5787342).

Almost surely, 2^21220243 is an apocalyptic number.

21220243 is a deficient number, since it is larger than the sum of its proper divisors (1929125).

21220243 is a wasteful number, since it uses less digits than its factorization.

21220243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1929124.

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21220243 is about 4606.5434981122. The cubic root of 21220243 is about 276.8535633351.

Adding to 21220243 its reverse (34202212), we get a palindrome (55422455).

The spelling of 21220243 in words is "twenty-one million, two hundred twenty thousand, two hundred forty-three".