21700243 has 2 divisors, whose sum is σ = 21700244. Its totient is φ = 21700242.

The previous prime is 21700219. The next prime is 21700253. The reversal of 21700243 is 34200712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21700243 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21700243.

It is not a weakly prime, because it can be changed into another prime (21700253) 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 as a sum of consecutive naturals, namely, 10850121 + 10850122.

It is an arithmetic number, because the mean of its divisors is an integer number (10850122).

Almost surely, 2^21700243 is an apocalyptic number.

21700243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21700243 is an equidigital number, since it uses as much as digits as its factorization.

21700243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21700243 is about 4658.3519617994. The cubic root of 21700243 is about 278.9254863682.

Adding to 21700243 its reverse (34200712), we get a palindrome (55900955).

The spelling of 21700243 in words is "twenty-one million, seven hundred thousand, two hundred forty-three".