3991072885721 has 2 divisors, whose sum is σ = 3991072885722. Its totient is φ = 3991072885720.

The previous prime is 3991072885717. The next prime is 3991072885829. The reversal of 3991072885721 is 1275882701993.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3952760304025 + 38312581696 = 1988155^2 + 195736^2 .

It is a cyclic number.

It is not a de Polignac number, because 3991072885721 - 2² = 3991072885717 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (3991072885321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995536442860 + 1995536442861.

It is an arithmetic number, because the mean of its divisors is an integer number (1995536442861).

Almost surely, 2^{3991072885721} is an apocalyptic number.

It is an amenable number.

3991072885721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991072885721 is an equidigital number, since it uses as much as digits as its factorization.

3991072885721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15240960, while the sum is 62.

The spelling of 3991072885721 in words is "three trillion, nine hundred ninety-one billion, seventy-two million, eight hundred eighty-five thousand, seven hundred twenty-one".