21958243 has 4 divisors (see below), whose sum is σ = 23113960. Its totient is φ = 20802528.

The previous prime is 21958229. The next prime is 21958267. The reversal of 21958243 is 34285912.

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 21958243 - 2¹⁷ = 21827171 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21958199 and 21958208.

It is not an unprimeable number, because it can be changed into a prime (21958213) 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, 577830 + ... + 577867.

It is an arithmetic number, because the mean of its divisors is an integer number (5778490).

Almost surely, 2^21958243 is an apocalyptic number.

21958243 is a deficient number, since it is larger than the sum of its proper divisors (1155717).

21958243 is a wasteful number, since it uses less digits than its factorization.

21958243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1155716.

The product of its digits is 17280, while the sum is 34.

The square root of 21958243 is about 4685.9623344624. The cubic root of 21958243 is about 280.0265408515.

It can be divided in two parts, 21958 and 243, that added together give a square (22201 = 149²).

The spelling of 21958243 in words is "twenty-one million, nine hundred fifty-eight thousand, two hundred forty-three".