3991319861 has 2 divisors, whose sum is σ = 3991319862. Its totient is φ = 3991319860.

The previous prime is 3991319831. The next prime is 3991319887. The reversal of 3991319861 is 1689131993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3648884836 + 342435025 = 60406^2 + 18505^2 .

It is a cyclic number.

It is not a de Polignac number, because 3991319861 - 2²² = 3987125557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3991319831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995659930 + 1995659931.

It is an arithmetic number, because the mean of its divisors is an integer number (1995659931).

Almost surely, 2^3991319861 is an apocalyptic number.

It is an amenable number.

3991319861 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991319861 is an equidigital number, since it uses as much as digits as its factorization.

3991319861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 314928, while the sum is 50.

The square root of 3991319861 is about 63176.8934104867. The cubic root of 3991319861 is about 1586.2519819113.

The spelling of 3991319861 in words is "three billion, nine hundred ninety-one million, three hundred nineteen thousand, eight hundred sixty-one".