21189899 has 2 divisors, whose sum is σ = 21189900. Its totient is φ = 21189898.

The previous prime is 21189827. The next prime is 21189913. The reversal of 21189899 is 99898112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21189899 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21189799) 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, 10594949 + 10594950.

It is an arithmetic number, because the mean of its divisors is an integer number (10594950).

Almost surely, 2^21189899 is an apocalyptic number.

21189899 is a deficient number, since it is larger than the sum of its proper divisors (1).

21189899 is an equidigital number, since it uses as much as digits as its factorization.

21189899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 93312, while the sum is 47.

The square root of 21189899 is about 4603.2487440937. The cubic root of 21189899 is about 276.7215376402.

It can be divided in two parts, 211898 and 99, that multiplied together give a palindrome (20977902).

The spelling of 21189899 in words is "twenty-one million, one hundred eighty-nine thousand, eight hundred ninety-nine".