20918197 has 2 divisors, whose sum is σ = 20918198. Its totient is φ = 20918196.

The previous prime is 20918189. The next prime is 20918203. The reversal of 20918197 is 79181902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20875761 + 42436 = 4569^2 + 206^2 .

It is a cyclic number.

It is not a de Polignac number, because 20918197 - 2³ = 20918189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20918497) 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, 10459098 + 10459099.

It is an arithmetic number, because the mean of its divisors is an integer number (10459099).

Almost surely, 2^20918197 is an apocalyptic number.

It is an amenable number.

20918197 is a deficient number, since it is larger than the sum of its proper divisors (1).

20918197 is an equidigital number, since it uses as much as digits as its factorization.

20918197 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 20918197 is about 4573.6415469514. The cubic root of 20918197 is about 275.5337161183.

It can be divided in two parts, 20918 and 197, that added together give a triangular number (21115 = T₂₀₅).

The spelling of 20918197 in words is "twenty million, nine hundred eighteen thousand, one hundred ninety-seven".