9981388121 has 2 divisors, whose sum is σ = 9981388122. Its totient is φ = 9981388120.

The previous prime is 9981388069. The next prime is 9981388133. The reversal of 9981388121 is 1218831899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9627534400 + 353853721 = 98120^2 + 18811^2 .

It is a cyclic number.

It is not a de Polignac number, because 9981388121 - 2²² = 9977193817 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9981388121.

It is not a weakly prime, because it can be changed into another prime (9981388621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4990694060 + 4990694061.

It is an arithmetic number, because the mean of its divisors is an integer number (4990694061).

Almost surely, 2^9981388121 is an apocalyptic number.

It is an amenable number.

9981388121 is a deficient number, since it is larger than the sum of its proper divisors (1).

9981388121 is an equidigital number, since it uses as much as digits as its factorization.

9981388121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 248832, while the sum is 50.

The square root of 9981388121 is about 99906.8972644031. The cubic root of 9981388121 is about 2153.0972573584.

The spelling of 9981388121 in words is "nine billion, nine hundred eighty-one million, three hundred eighty-eight thousand, one hundred twenty-one".