3947811991 has 2 divisors, whose sum is σ = 3947811992. Its totient is φ = 3947811990.

The previous prime is 3947811941. The next prime is 3947811997. The reversal of 3947811991 is 1991187493.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 3947811991 - 2¹³ = 3947803799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3947811997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1973905995 + 1973905996.

It is an arithmetic number, because the mean of its divisors is an integer number (1973905996).

Almost surely, 2^3947811991 is an apocalyptic number.

3947811991 is a deficient number, since it is larger than the sum of its proper divisors (1).

3947811991 is an equidigital number, since it uses as much as digits as its factorization.

3947811991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 489888, while the sum is 52.

The square root of 3947811991 is about 62831.6161737067. The cubic root of 3947811991 is about 1580.4672002710.

The spelling of 3947811991 in words is "three billion, nine hundred forty-seven million, eight hundred eleven thousand, nine hundred ninety-one".