21047237 has 2 divisors, whose sum is σ = 21047238. Its totient is φ = 21047236.

The previous prime is 21047209. The next prime is 21047281. The reversal of 21047237 is 73274012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19061956 + 1985281 = 4366^2 + 1409^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21047237 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21043237) 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, 10523618 + 10523619.

It is an arithmetic number, because the mean of its divisors is an integer number (10523619).

Almost surely, 2^21047237 is an apocalyptic number.

It is an amenable number.

21047237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21047237 is an equidigital number, since it uses as much as digits as its factorization.

21047237 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 21047237 is about 4587.7267791358. The cubic root of 21047237 is about 276.0991251106.

The spelling of 21047237 in words is "twenty-one million, forty-seven thousand, two hundred thirty-seven".