991840643 has 2 divisors, whose sum is σ = 991840644. Its totient is φ = 991840642.

The previous prime is 991840627. The next prime is 991840657. The reversal of 991840643 is 346048199.

991840643 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991840643 - 2⁴ = 991840627 is a prime.

It is a super-3 number, since 3×991840643³ (a number of 28 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 991840594 and 991840603.

It is not a weakly prime, because it can be changed into another prime (991840613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495920321 + 495920322.

It is an arithmetic number, because the mean of its divisors is an integer number (495920322).

Almost surely, 2^991840643 is an apocalyptic number.

991840643 is a deficient number, since it is larger than the sum of its proper divisors (1).

991840643 is an equidigital number, since it uses as much as digits as its factorization.

991840643 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 186624, while the sum is 44.

The square root of 991840643 is about 31493.5015995364. The cubic root of 991840643 is about 997.2727833843.

The spelling of 991840643 in words is "nine hundred ninety-one million, eight hundred forty thousand, six hundred forty-three".