21197129 has 2 divisors, whose sum is σ = 21197130. Its totient is φ = 21197128.

The previous prime is 21197117. The next prime is 21197131. The reversal of 21197129 is 92179112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20457529 + 739600 = 4523^2 + 860^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21197129 is a prime.

Together with 21197131, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21197095 and 21197104.

It is not a weakly prime, because it can be changed into another prime (21197159) 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, 10598564 + 10598565.

It is an arithmetic number, because the mean of its divisors is an integer number (10598565).

Almost surely, 2^21197129 is an apocalyptic number.

It is an amenable number.

21197129 is a deficient number, since it is larger than the sum of its proper divisors (1).

21197129 is an equidigital number, since it uses as much as digits as its factorization.

21197129 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2268, while the sum is 32.

The square root of 21197129 is about 4604.0339920552. The cubic root of 21197129 is about 276.7530065524.

The spelling of 21197129 in words is "twenty-one million, one hundred ninety-seven thousand, one hundred twenty-nine".