21980243 has 2 divisors, whose sum is σ = 21980244. Its totient is φ = 21980242.

The previous prime is 21980197. The next prime is 21980281. The reversal of 21980243 is 34208912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21980243 - 2¹⁶ = 21914707 is a prime.

It is not a weakly prime, because it can be changed into another prime (21980293) 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, 10990121 + 10990122.

It is an arithmetic number, because the mean of its divisors is an integer number (10990122).

Almost surely, 2^21980243 is an apocalyptic number.

21980243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21980243 is an equidigital number, since it uses as much as digits as its factorization.

21980243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21980243 is about 4688.3091834904. The cubic root of 21980243 is about 280.1200293213.

The spelling of 21980243 in words is "twenty-one million, nine hundred eighty thousand, two hundred forty-three".