21129799 has 2 divisors, whose sum is σ = 21129800. Its totient is φ = 21129798.

The previous prime is 21129791. The next prime is 21129803. The reversal of 21129799 is 99792112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21129799 - 2³ = 21129791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21129791) 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, 10564899 + 10564900.

It is an arithmetic number, because the mean of its divisors is an integer number (10564900).

Almost surely, 2^21129799 is an apocalyptic number.

21129799 is a deficient number, since it is larger than the sum of its proper divisors (1).

21129799 is an equidigital number, since it uses as much as digits as its factorization.

21129799 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20412, while the sum is 40.

The square root of 21129799 is about 4596.7161104423. The cubic root of 21129799 is about 276.4596721091.

It can be divided in two parts, 2112 and 9799, that added together give a palindrome (11911).

The spelling of 21129799 in words is "twenty-one million, one hundred twenty-nine thousand, seven hundred ninety-nine".