21109867 has 2 divisors, whose sum is σ = 21109868. Its totient is φ = 21109866.

The previous prime is 21109841. The next prime is 21109871. The reversal of 21109867 is 76890112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21109867 is a prime.

It is not a weakly prime, because it can be changed into another prime (21109877) 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, 10554933 + 10554934.

It is an arithmetic number, because the mean of its divisors is an integer number (10554934).

Almost surely, 2^21109867 is an apocalyptic number.

21109867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109867 is an equidigital number, since it uses as much as digits as its factorization.

21109867 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21109867 is about 4594.5475294092. The cubic root of 21109867 is about 276.3727154882.

Adding to 21109867 its reverse (76890112), we get a palindrome (97999979).

The spelling of 21109867 in words is "twenty-one million, one hundred nine thousand, eight hundred sixty-seven".