990921791 has 2 divisors, whose sum is σ = 990921792. Its totient is φ = 990921790.

The previous prime is 990921787. The next prime is 990921829. The reversal of 990921791 is 197129099.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (197129099) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 990921791 - 2² = 990921787 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (990921731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495460895 + 495460896.

It is an arithmetic number, because the mean of its divisors is an integer number (495460896).

Almost surely, 2^990921791 is an apocalyptic number.

990921791 is a deficient number, since it is larger than the sum of its proper divisors (1).

990921791 is an equidigital number, since it uses as much as digits as its factorization.

990921791 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 91854, while the sum is 47.

The square root of 990921791 is about 31478.9102575042. The cubic root of 990921791 is about 996.9647267710.

The spelling of 990921791 in words is "nine hundred ninety million, nine hundred twenty-one thousand, seven hundred ninety-one".