20897509 has 2 divisors, whose sum is σ = 20897510. Its totient is φ = 20897508.

The previous prime is 20897497. The next prime is 20897519. The reversal of 20897509 is 90579802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10956100 + 9941409 = 3310^2 + 3153^2 .

It is a cyclic number.

It is not a de Polignac number, because 20897509 - 2⁵ = 20897477 is a prime.

It is a zygodrome in base 3.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20897519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10448754 + 10448755.

It is an arithmetic number, because the mean of its divisors is an integer number (10448755).

Almost surely, 2^20897509 is an apocalyptic number.

It is an amenable number.

20897509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20897509 is an equidigital number, since it uses as much as digits as its factorization.

20897509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 45360, while the sum is 40.

The square root of 20897509 is about 4571.3793323241. The cubic root of 20897509 is about 275.4428523005.

The spelling of 20897509 in words is "twenty million, eight hundred ninety-seven thousand, five hundred nine".