3865105721 has 2 divisors, whose sum is σ = 3865105722. Its totient is φ = 3865105720.

The previous prime is 3865105667. The next prime is 3865105733. The reversal of 3865105721 is 1275015683.

3865105721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2799997225 + 1065108496 = 52915^2 + 32636^2 .

It is a cyclic number.

It is not a de Polignac number, because 3865105721 - 2²⁶ = 3797996857 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 (3865105121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1932552860 + 1932552861.

It is an arithmetic number, because the mean of its divisors is an integer number (1932552861).

Almost surely, 2^3865105721 is an apocalyptic number.

It is an amenable number.

3865105721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3865105721 is an equidigital number, since it uses as much as digits as its factorization.

3865105721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 50400, while the sum is 38.

The square root of 3865105721 is about 62169.9744330010. The cubic root of 3865105721 is about 1569.3523395941.

The spelling of 3865105721 in words is "three billion, eight hundred sixty-five million, one hundred five thousand, seven hundred twenty-one".