21278911 has 2 divisors, whose sum is σ = 21278912. Its totient is φ = 21278910.

The previous prime is 21278899. The next prime is 21278923. The reversal of 21278911 is 11987212.

It is a balanced prime because it is at equal distance from previous prime (21278899) and next prime (21278923).

It is a cyclic number.

It is not a de Polignac number, because 21278911 - 2⁹ = 21278399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21278941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639455 + 10639456.

It is an arithmetic number, because the mean of its divisors is an integer number (10639456).

Almost surely, 2^21278911 is an apocalyptic number.

21278911 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278911 is an equidigital number, since it uses as much as digits as its factorization.

21278911 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 31.

The square root of 21278911 is about 4612.9070010136. The cubic root of 21278911 is about 277.1084692946.

The spelling of 21278911 in words is "twenty-one million, two hundred seventy-eight thousand, nine hundred eleven".