20978197 has 2 divisors, whose sum is σ = 20978198. Its totient is φ = 20978196.

The previous prime is 20978189. The next prime is 20978201. The reversal of 20978197 is 79187902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20439441 + 538756 = 4521^2 + 734^2 .

It is a cyclic number.

It is not a de Polignac number, because 20978197 - 2³ = 20978189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20978117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10489098 + 10489099.

It is an arithmetic number, because the mean of its divisors is an integer number (10489099).

Almost surely, 2^20978197 is an apocalyptic number.

It is an amenable number.

20978197 is a deficient number, since it is larger than the sum of its proper divisors (1).

20978197 is an equidigital number, since it uses as much as digits as its factorization.

20978197 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20978197 is about 4580.1961748379. The cubic root of 20978197 is about 275.7969039024.

The spelling of 20978197 in words is "twenty million, nine hundred seventy-eight thousand, one hundred ninety-seven".