21507289 has 2 divisors, whose sum is σ = 21507290. Its totient is φ = 21507288.

The previous prime is 21507287. The next prime is 21507307. The reversal of 21507289 is 98270512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14953689 + 6553600 = 3867^2 + 2560^2 .

It is a cyclic number.

It is not a de Polignac number, because 21507289 - 2¹ = 21507287 is a prime.

Together with 21507287, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21507281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753644 + 10753645.

It is an arithmetic number, because the mean of its divisors is an integer number (10753645).

Almost surely, 2^21507289 is an apocalyptic number.

It is an amenable number.

21507289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21507289 is an equidigital number, since it uses as much as digits as its factorization.

21507289 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 21507289 is about 4637.5951742255. The cubic root of 21507289 is about 278.0963082636.

The spelling of 21507289 in words is "twenty-one million, five hundred seven thousand, two hundred eighty-nine".