21210197 has 2 divisors, whose sum is σ = 21210198. Its totient is φ = 21210196.

The previous prime is 21210193. The next prime is 21210221. The reversal of 21210197 is 79101212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10719076 + 10491121 = 3274^2 + 3239^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210197 - 2² = 21210193 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210193) 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, 10605098 + 10605099.

It is an arithmetic number, because the mean of its divisors is an integer number (10605099).

Almost surely, 2^21210197 is an apocalyptic number.

It is an amenable number.

21210197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210197 is an equidigital number, since it uses as much as digits as its factorization.

21210197 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21210197 is about 4605.4529636074. The cubic root of 21210197 is about 276.8098674813.

The spelling of 21210197 in words is "twenty-one million, two hundred ten thousand, one hundred ninety-seven".