21005297 has 2 divisors, whose sum is σ = 21005298. Its totient is φ = 21005296.

The previous prime is 21005293. The next prime is 21005311. The reversal of 21005297 is 79250012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11999296 + 9006001 = 3464^2 + 3001^2 .

It is a cyclic number.

It is not a de Polignac number, because 21005297 - 2² = 21005293 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21005291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502648 + 10502649.

It is an arithmetic number, because the mean of its divisors is an integer number (10502649).

Almost surely, 2^21005297 is an apocalyptic number.

It is an amenable number.

21005297 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005297 is an equidigital number, since it uses as much as digits as its factorization.

21005297 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1260, while the sum is 26.

The square root of 21005297 is about 4583.1536085975. The cubic root of 21005297 is about 275.9156125473.

The spelling of 21005297 in words is "twenty-one million, five thousand, two hundred ninety-seven".