21340243 has 2 divisors, whose sum is σ = 21340244. Its totient is φ = 21340242.

The previous prime is 21340223. The next prime is 21340247. The reversal of 21340243 is 34204312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21340243 - 2¹⁷ = 21209171 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21340243.

It is not a weakly prime, because it can be changed into another prime (21340247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10670121 + 10670122.

It is an arithmetic number, because the mean of its divisors is an integer number (10670122).

Almost surely, 2^21340243 is an apocalyptic number.

21340243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21340243 is an equidigital number, since it uses as much as digits as its factorization.

21340243 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 21340243 is about 4619.5500863179. The cubic root of 21340243 is about 277.3744496036.

Adding to 21340243 its reverse (34204312), we get a palindrome (55544555).

The spelling of 21340243 in words is "twenty-one million, three hundred forty thousand, two hundred forty-three".