3971428721 has 4 divisors (see below), whose sum is σ = 4276923252. Its totient is φ = 3665934192.

The previous prime is 3971428717. The next prime is 3971428723. The reversal of 3971428721 is 1278241793.

3971428721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1094286400 + 2877142321 = 33080^2 + 53639^2 .

It is a cyclic number.

It is not a de Polignac number, because 3971428721 - 2² = 3971428717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3971428723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 152747246 + ... + 152747271.

It is an arithmetic number, because the mean of its divisors is an integer number (1069230813).

Almost surely, 2^3971428721 is an apocalyptic number.

It is an amenable number.

3971428721 is a deficient number, since it is larger than the sum of its proper divisors (305494531).

3971428721 is a wasteful number, since it uses less digits than its factorization.

3971428721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305494530.

The product of its digits is 169344, while the sum is 44.

The square root of 3971428721 is about 63019.2726156055. The cubic root of 3971428721 is about 1583.6125107817.

The spelling of 3971428721 in words is "three billion, nine hundred seventy-one million, four hundred twenty-eight thousand, seven hundred twenty-one".