991722871 has 2 divisors, whose sum is σ = 991722872. Its totient is φ = 991722870.

The previous prime is 991722869. The next prime is 991722881. The reversal of 991722871 is 178227199.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991722871 - 2¹ = 991722869 is a prime.

Together with 991722869, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991722881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495861435 + 495861436.

It is an arithmetic number, because the mean of its divisors is an integer number (495861436).

Almost surely, 2^991722871 is an apocalyptic number.

991722871 is a deficient number, since it is larger than the sum of its proper divisors (1).

991722871 is an equidigital number, since it uses as much as digits as its factorization.

991722871 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008, while the sum is 46.

The square root of 991722871 is about 31491.6317614696. The cubic root of 991722871 is about 997.2333094829.

The spelling of 991722871 in words is "nine hundred ninety-one million, seven hundred twenty-two thousand, eight hundred seventy-one".