21237289 has 2 divisors, whose sum is σ = 21237290. Its totient is φ = 21237288.

The previous prime is 21237287. The next prime is 21237311. The reversal of 21237289 is 98273212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16362025 + 4875264 = 4045^2 + 2208^2 .

It is a cyclic number.

It is not a de Polignac number, because 21237289 - 2¹ = 21237287 is a prime.

Together with 21237287, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21237287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10618644 + 10618645.

It is an arithmetic number, because the mean of its divisors is an integer number (10618645).

Almost surely, 2^21237289 is an apocalyptic number.

It is an amenable number.

21237289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21237289 is an equidigital number, since it uses as much as digits as its factorization.

21237289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 34.

The square root of 21237289 is about 4608.3933208874. The cubic root of 21237289 is about 276.9276746882.

The spelling of 21237289 in words is "twenty-one million, two hundred thirty-seven thousand, two hundred eighty-nine".