21520297 has 2 divisors, whose sum is σ = 21520298. Its totient is φ = 21520296.

The previous prime is 21520271. The next prime is 21520307. The reversal of 21520297 is 79202512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19501056 + 2019241 = 4416^2 + 1421^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520297 - 2¹⁹ = 20996009 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21520207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760148 + 10760149.

It is an arithmetic number, because the mean of its divisors is an integer number (10760149).

Almost surely, 2^21520297 is an apocalyptic number.

It is an amenable number.

21520297 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520297 is an equidigital number, since it uses as much as digits as its factorization.

21520297 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21520297 is about 4638.9974132349. The cubic root of 21520297 is about 278.1523628678.

The spelling of 21520297 in words is "twenty-one million, five hundred twenty thousand, two hundred ninety-seven".