21042851 has 2 divisors, whose sum is σ = 21042852. Its totient is φ = 21042850.

The previous prime is 21042841. The next prime is 21042863. The reversal of 21042851 is 15824012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21042851 - 2¹⁰ = 21041827 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21042841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521425 + 10521426.

It is an arithmetic number, because the mean of its divisors is an integer number (10521426).

Almost surely, 2^21042851 is an apocalyptic number.

21042851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042851 is an equidigital number, since it uses as much as digits as its factorization.

21042851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21042851 is about 4587.2487397132. The cubic root of 21042851 is about 276.0799451601.

Adding to 21042851 its reverse (15824012), we get a palindrome (36866863).

The spelling of 21042851 in words is "twenty-one million, forty-two thousand, eight hundred fifty-one".