9999555551 has 2 divisors, whose sum is σ = 9999555552. Its totient is φ = 9999555550.

The previous prime is 9999555541. The next prime is 9999555613. The reversal of 9999555551 is 1555559999.

9999555551 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (9999555613) can be obtained adding 9999555551 to its sum of digits (62).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9999555551 - 2¹⁴ = 9999539167 is a prime.

It is a super-2 number, since 2×9999555551² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9999555541) 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, 4999777775 + 4999777776.

It is an arithmetic number, because the mean of its divisors is an integer number (4999777776).

Almost surely, 2^9999555551 is an apocalyptic number.

9999555551 is a deficient number, since it is larger than the sum of its proper divisors (1).

9999555551 is an equidigital number, since it uses as much as digits as its factorization.

9999555551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20503125, while the sum is 62.

The square root of 9999555551 is about 99997.7777303076. Note that the first 4 decimals coincide. The cubic root of 9999555551 is about 2154.4027716809.

The spelling of 9999555551 in words is "nine billion, nine hundred ninety-nine million, five hundred fifty-five thousand, five hundred fifty-one".