21237287 has 2 divisors, whose sum is σ = 21237288. Its totient is φ = 21237286.

The previous prime is 21237241. The next prime is 21237289. The reversal of 21237287 is 78273212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21237287 - 2⁸ = 21237031 is a prime.

Together with 21237289, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21237289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10618643 + 10618644.

It is an arithmetic number, because the mean of its divisors is an integer number (10618644).

Almost surely, 2^21237287 is an apocalyptic number.

21237287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21237287 is an equidigital number, since it uses as much as digits as its factorization.

21237287 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 32.

The square root of 21237287 is about 4608.3931038921. The cubic root of 21237287 is about 276.9276659951.

The spelling of 21237287 in words is "twenty-one million, two hundred thirty-seven thousand, two hundred eighty-seven".