21730249 has 2 divisors, whose sum is σ = 21730250. Its totient is φ = 21730248.

The previous prime is 21730169. The next prime is 21730273. The reversal of 21730249 is 94203712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12027024 + 9703225 = 3468^2 + 3115^2 .

It is a cyclic number.

It is not a de Polignac number, because 21730249 - 2¹⁷ = 21599177 is a prime.

It is not a weakly prime, because it can be changed into another prime (21730649) 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, 10865124 + 10865125.

It is an arithmetic number, because the mean of its divisors is an integer number (10865125).

Almost surely, 2^21730249 is an apocalyptic number.

It is an amenable number.

21730249 is a deficient number, since it is larger than the sum of its proper divisors (1).

21730249 is an equidigital number, since it uses as much as digits as its factorization.

21730249 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21730249 is about 4661.5715161306. The cubic root of 21730249 is about 279.0539885159.

The spelling of 21730249 in words is "twenty-one million, seven hundred thirty thousand, two hundred forty-nine".