9781988556541 has 2 divisors, whose sum is σ = 9781988556542. Its totient is φ = 9781988556540.

The previous prime is 9781988556517. The next prime is 9781988556553. The reversal of 9781988556541 is 1456558891879.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9706901048100 + 75087508441 = 3115590^2 + 274021^2 .

It is a cyclic number.

It is not a de Polignac number, because 9781988556541 - 2⁷ = 9781988556413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9781988556511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4890994278270 + 4890994278271.

It is an arithmetic number, because the mean of its divisors is an integer number (4890994278271).

Almost surely, 2^{9781988556541} is an apocalyptic number.

It is an amenable number.

9781988556541 is a deficient number, since it is larger than the sum of its proper divisors (1).

9781988556541 is an equidigital number, since it uses as much as digits as its factorization.

9781988556541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 870912000, while the sum is 76.

The spelling of 9781988556541 in words is "nine trillion, seven hundred eighty-one billion, nine hundred eighty-eight million, five hundred fifty-six thousand, five hundred forty-one".