3938871721 has 2 divisors, whose sum is σ = 3938871722. Its totient is φ = 3938871720.

The previous prime is 3938871709. The next prime is 3938871737. The reversal of 3938871721 is 1271788393.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3936182121 + 2689600 = 62739^2 + 1640^2 .

It is an emirp because it is prime and its reverse (1271788393) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3938871721 - 2²⁵ = 3905317289 is a prime.

It is a super-3 number, since 3×3938871721³ (a number of 30 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (3938871701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1969435860 + 1969435861.

It is an arithmetic number, because the mean of its divisors is an integer number (1969435861).

Almost surely, 2^3938871721 is an apocalyptic number.

It is an amenable number.

3938871721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3938871721 is an equidigital number, since it uses as much as digits as its factorization.

3938871721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 508032, while the sum is 49.

The square root of 3938871721 is about 62760.4311728337. The cubic root of 3938871721 is about 1579.2732491953.

The spelling of 3938871721 in words is "three billion, nine hundred thirty-eight million, eight hundred seventy-one thousand, seven hundred twenty-one".