940821991 has 2 divisors, whose sum is σ = 940821992. Its totient is φ = 940821990.

The previous prime is 940821989. The next prime is 940822021. The reversal of 940821991 is 199128049.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 940821991 - 2¹ = 940821989 is a prime.

Together with 940821989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (940821901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 470410995 + 470410996.

It is an arithmetic number, because the mean of its divisors is an integer number (470410996).

Almost surely, 2^940821991 is an apocalyptic number.

940821991 is a deficient number, since it is larger than the sum of its proper divisors (1).

940821991 is an equidigital number, since it uses as much as digits as its factorization.

940821991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 46656, while the sum is 43.

The square root of 940821991 is about 30672.8216993481. The cubic root of 940821991 is about 979.8715613295.

The spelling of 940821991 in words is "nine hundred forty million, eight hundred twenty-one thousand, nine hundred ninety-one".