991649505851 has 2 divisors, whose sum is σ = 991649505852. Its totient is φ = 991649505850.

The previous prime is 991649505829. The next prime is 991649505919. The reversal of 991649505851 is 158505946199.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991649505851 - 2⁶ = 991649505787 is a prime.

It is not a weakly prime, because it can be changed into another prime (991649507851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495824752925 + 495824752926.

It is an arithmetic number, because the mean of its divisors is an integer number (495824752926).

Almost surely, 2^991649505851 is an apocalyptic number.

991649505851 is a deficient number, since it is larger than the sum of its proper divisors (1).

991649505851 is an equidigital number, since it uses as much as digits as its factorization.

991649505851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17496000, while the sum is 62.

The spelling of 991649505851 in words is "nine hundred ninety-one billion, six hundred forty-nine million, five hundred five thousand, eight hundred fifty-one".