21320197 has 2 divisors, whose sum is σ = 21320198. Its totient is φ = 21320196.

The previous prime is 21320183. The next prime is 21320203. The reversal of 21320197 is 79102312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19088161 + 2232036 = 4369^2 + 1494^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320197 - 2¹¹ = 21318149 is a prime.

It is a super-3 number, since 3×21320197³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21320107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660098 + 10660099.

It is an arithmetic number, because the mean of its divisors is an integer number (10660099).

Almost surely, 2^21320197 is an apocalyptic number.

It is an amenable number.

21320197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320197 is an equidigital number, since it uses as much as digits as its factorization.

21320197 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21320197 is about 4617.3798847398. The cubic root of 21320197 is about 277.2875716467.

The spelling of 21320197 in words is "twenty-one million, three hundred twenty thousand, one hundred ninety-seven".