991900909847 has 2 divisors, whose sum is σ = 991900909848. Its totient is φ = 991900909846.

The previous prime is 991900909781. The next prime is 991900909859. The reversal of 991900909847 is 748909009199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991900909847 - 2⁸ = 991900909591 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991900909877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495950454923 + 495950454924.

It is an arithmetic number, because the mean of its divisors is an integer number (495950454924).

Almost surely, 2^991900909847 is an apocalyptic number.

991900909847 is a deficient number, since it is larger than the sum of its proper divisors (1).

991900909847 is an equidigital number, since it uses as much as digits as its factorization.

991900909847 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13226976, while the sum is 65.

The spelling of 991900909847 in words is "nine hundred ninety-one billion, nine hundred million, nine hundred nine thousand, eight hundred forty-seven".