20218688981 has 2 divisors, whose sum is σ = 20218688982. Its totient is φ = 20218688980.

The previous prime is 20218688929. The next prime is 20218688993. The reversal of 20218688981 is 18988681202.

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., 12953854225 + 7264834756 = 113815^2 + 85234^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20218688981 is a prime.

It is a super-2 number, since 2×20218688981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20215688981) 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, 10109344490 + 10109344491.

It is an arithmetic number, because the mean of its divisors is an integer number (10109344491).

Almost surely, 2^20218688981 is an apocalyptic number.

It is an amenable number.

20218688981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20218688981 is an equidigital number, since it uses as much as digits as its factorization.

20218688981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 884736, while the sum is 53.

The spelling of 20218688981 in words is "twenty billion, two hundred eighteen million, six hundred eighty-eight thousand, nine hundred eighty-one".