3981720643 has 2 divisors, whose sum is σ = 3981720644. Its totient is φ = 3981720642.

The previous prime is 3981720629. The next prime is 3981720709. The reversal of 3981720643 is 3460271893.

3981720643 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3981720643 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 3981720643.

It is not a weakly prime, because it can be changed into another prime (3981720143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1990860321 + 1990860322.

It is an arithmetic number, because the mean of its divisors is an integer number (1990860322).

Almost surely, 2^3981720643 is an apocalyptic number.

3981720643 is a deficient number, since it is larger than the sum of its proper divisors (1).

3981720643 is an equidigital number, since it uses as much as digits as its factorization.

3981720643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 43.

The square root of 3981720643 is about 63100.8767213261. The cubic root of 3981720643 is about 1584.9793033351.

The spelling of 3981720643 in words is "three billion, nine hundred eighty-one million, seven hundred twenty thousand, six hundred forty-three".