991555199 has 2 divisors, whose sum is σ = 991555200. Its totient is φ = 991555198.

The previous prime is 991555171. The next prime is 991555207.

991555199 is nontrivially palindromic in base 10.

It is a strong prime.

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 991555199 - 2²⁴ = 974777983 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 991555199.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991555129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495777599 + 495777600.

It is an arithmetic number, because the mean of its divisors is an integer number (495777600).

Almost surely, 2^991555199 is an apocalyptic number.

991555199 is a deficient number, since it is larger than the sum of its proper divisors (1).

991555199 is an equidigital number, since it uses as much as digits as its factorization.

991555199 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 820125, while the sum is 53.

The square root of 991555199 is about 31488.9694813914. The cubic root of 991555199 is about 997.1771050960.

The spelling of 991555199 in words is "nine hundred ninety-one million, five hundred fifty-five thousand, one hundred ninety-nine".