9991438549 has 2 divisors, whose sum is σ = 9991438550. Its totient is φ = 9991438548.

The previous prime is 9991438531. The next prime is 9991438559. The reversal of 9991438549 is 9458341999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9896668324 + 94770225 = 99482^2 + 9735^2 .

It is a cyclic number.

It is not a de Polignac number, because 9991438549 - 2¹⁷ = 9991307477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9991438529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995719274 + 4995719275.

It is an arithmetic number, because the mean of its divisors is an integer number (4995719275).

Almost surely, 2^9991438549 is an apocalyptic number.

It is an amenable number.

9991438549 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991438549 is an equidigital number, since it uses as much as digits as its factorization.

9991438549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12597120, while the sum is 61.

The square root of 9991438549 is about 99957.1835787704. The cubic root of 9991438549 is about 2153.8196782510.

The spelling of 9991438549 in words is "nine billion, nine hundred ninety-one million, four hundred thirty-eight thousand, five hundred forty-nine".