21138851 has 2 divisors, whose sum is σ = 21138852. Its totient is φ = 21138850.

The previous prime is 21138847. The next prime is 21138853. The reversal of 21138851 is 15883112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21138851 - 2² = 21138847 is a prime.

Together with 21138853, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21138853) 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, 10569425 + 10569426.

It is an arithmetic number, because the mean of its divisors is an integer number (10569426).

Almost surely, 2^21138851 is an apocalyptic number.

21138851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138851 is an equidigital number, since it uses as much as digits as its factorization.

21138851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 29.

The square root of 21138851 is about 4597.7006209626. The cubic root of 21138851 is about 276.4991448884.

The spelling of 21138851 in words is "twenty-one million, one hundred thirty-eight thousand, eight hundred fifty-one".