991638133 has 2 divisors, whose sum is σ = 991638134. Its totient is φ = 991638132.

The previous prime is 991638107. The next prime is 991638157. The reversal of 991638133 is 331836199.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 959636484 + 32001649 = 30978^2 + 5657^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991638133 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 991638133.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991638163) 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, 495819066 + 495819067.

It is an arithmetic number, because the mean of its divisors is an integer number (495819067).

Almost surely, 2^991638133 is an apocalyptic number.

It is an amenable number.

991638133 is a deficient number, since it is larger than the sum of its proper divisors (1).

991638133 is an equidigital number, since it uses as much as digits as its factorization.

991638133 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 104976, while the sum is 43.

The square root of 991638133 is about 31490.2863276916. The cubic root of 991638133 is about 997.2049057269.

The spelling of 991638133 in words is "nine hundred ninety-one million, six hundred thirty-eight thousand, one hundred thirty-three".