20021855371897 has 2 divisors, whose sum is σ = 20021855371898. Its totient is φ = 20021855371896.

The previous prime is 20021855371867. The next prime is 20021855371907. The reversal of 20021855371897 is 79817355812002.

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., 10475553667216 + 9546301704681 = 3236596^2 + 3089709^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20021855371897 is a prime.

It is not a weakly prime, because it can be changed into another prime (20021855371867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010927685948 + 10010927685949.

It is an arithmetic number, because the mean of its divisors is an integer number (10010927685949).

Almost surely, 2^{20021855371897} is an apocalyptic number.

It is an amenable number.

20021855371897 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021855371897 is an equidigital number, since it uses as much as digits as its factorization.

20021855371897 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8467200, while the sum is 58.

The spelling of 20021855371897 in words is "twenty trillion, twenty-one billion, eight hundred fifty-five million, three hundred seventy-one thousand, eight hundred ninety-seven".