3900686721 has 4 divisors (see below), whose sum is σ = 5200915632. Its totient is φ = 2600457812.

The previous prime is 3900686707. The next prime is 3900686723. The reversal of 3900686721 is 1276860093.

It is a happy number.

3900686721 is digitally balanced in base 2, 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, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1276860093 = 3 ⋅425620031.

It is a cyclic number.

It is not a de Polignac number, because 3900686721 - 2⁵ = 3900686689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (3900686723) 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, 650114451 + ... + 650114456.

It is an arithmetic number, because the mean of its divisors is an integer number (1300228908).

Almost surely, 2^3900686721 is an apocalyptic number.

It is an amenable number.

3900686721 is a deficient number, since it is larger than the sum of its proper divisors (1300228911).

3900686721 is a wasteful number, since it uses less digits than its factorization.

3900686721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1300228910.

The product of its (nonzero) digits is 108864, while the sum is 42.

The square root of 3900686721 is about 62455.4779102682. The cubic root of 3900686721 is about 1574.1532993022.

The spelling of 3900686721 in words is "three billion, nine hundred million, six hundred eighty-six thousand, seven hundred twenty-one".