2004021991 has 2 divisors, whose sum is σ = 2004021992. Its totient is φ = 2004021990.

The previous prime is 2004021977. The next prime is 2004022043. The reversal of 2004021991 is 1991204002.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2004021991 - 2²⁹ = 1467151079 is a prime.

It is a super-2 number, since 2×2004021991² = 8032208280823208162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2004021091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1002010995 + 1002010996.

It is an arithmetic number, because the mean of its divisors is an integer number (1002010996).

Almost surely, 2^2004021991 is an apocalyptic number.

2004021991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2004021991 is an equidigital number, since it uses as much as digits as its factorization.

2004021991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 2004021991 is about 44766.3041918807. The cubic root of 2004021991 is about 1260.7650495748.

Adding to 2004021991 its reverse (1991204002), we get a palindrome (3995225993).

The spelling of 2004021991 in words is "two billion, four million, twenty-one thousand, nine hundred ninety-one".