21128851 has 2 divisors, whose sum is σ = 21128852. Its totient is φ = 21128850.

The previous prime is 21128843. The next prime is 21128869. The reversal of 21128851 is 15882112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21128851 - 2³ = 21128843 is a prime.

It is equal to p_1337608 and since 21128851 and 1337608 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21126851) 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, 10564425 + 10564426.

It is an arithmetic number, because the mean of its divisors is an integer number (10564426).

Almost surely, 2^21128851 is an apocalyptic number.

21128851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21128851 is an equidigital number, since it uses as much as digits as its factorization.

21128851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1280, while the sum is 28.

The square root of 21128851 is about 4596.6129921933. The cubic root of 21128851 is about 276.4555375425.

The spelling of 21128851 in words is "twenty-one million, one hundred twenty-eight thousand, eight hundred fifty-one".