20938449818857 has 2 divisors, whose sum is σ = 20938449818858. Its totient is φ = 20938449818856.

The previous prime is 20938449818827. The next prime is 20938449818893. The reversal of 20938449818857 is 75881894483902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14332501217241 + 6605948601616 = 3785829^2 + 2570204^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20938449818857 is a prime.

It is a super-2 number, since 2×20938449818857² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20938449818807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10469224909428 + 10469224909429.

It is an arithmetic number, because the mean of its divisors is an integer number (10469224909429).

Almost surely, 2^{20938449818857} is an apocalyptic number.

It is an amenable number.

20938449818857 is a deficient number, since it is larger than the sum of its proper divisors (1).

20938449818857 is an equidigital number, since it uses as much as digits as its factorization.

20938449818857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1114767360, while the sum is 76.

The spelling of 20938449818857 in words is "twenty trillion, nine hundred thirty-eight billion, four hundred forty-nine million, eight hundred eighteen thousand, eight hundred fifty-seven".