21395243 has 4 divisors (see below), whose sum is σ = 22133040. Its totient is φ = 20657448.

The previous prime is 21395219. The next prime is 21395249. The reversal of 21395243 is 34259312.

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 21395243 - 2²⁴ = 4618027 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 737767 = 21395243 / (2 + 1 + 3 + 9 + 5 + 2 + 4 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21395249) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 368855 + ... + 368912.

It is an arithmetic number, because the mean of its divisors is an integer number (5533260).

Almost surely, 2^21395243 is an apocalyptic number.

21395243 is a deficient number, since it is larger than the sum of its proper divisors (737797).

21395243 is an equidigital number, since it uses as much as digits as its factorization.

21395243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 737796.

The product of its digits is 6480, while the sum is 29.

The square root of 21395243 is about 4625.4992163009. The cubic root of 21395243 is about 277.6125366680.

The spelling of 21395243 in words is "twenty-one million, three hundred ninety-five thousand, two hundred forty-three".