21168397 has 2 divisors, whose sum is σ = 21168398. Its totient is φ = 21168396.

The previous prime is 21168391. The next prime is 21168409. The reversal of 21168397 is 79386112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19900521 + 1267876 = 4461^2 + 1126^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21168397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21168391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10584198 + 10584199.

It is an arithmetic number, because the mean of its divisors is an integer number (10584199).

Almost surely, 2^21168397 is an apocalyptic number.

It is an amenable number.

21168397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21168397 is an equidigital number, since it uses as much as digits as its factorization.

21168397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 21168397 is about 4600.9126268600. The cubic root of 21168397 is about 276.6279068619.

The spelling of 21168397 in words is "twenty-one million, one hundred sixty-eight thousand, three hundred ninety-seven".