3938721 has 4 divisors (see below), whose sum is σ = 5251632. Its totient is φ = 2625812.

The previous prime is 3938717. The next prime is 3938723. The reversal of 3938721 is 1278393.

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: 1278393 = 3 ⋅426131.

It is a cyclic number.

It is not a de Polignac number, because 3938721 - 2² = 3938717 is a prime.

It is an Ulam number.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (3938723) 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, 656451 + ... + 656456.

It is an arithmetic number, because the mean of its divisors is an integer number (1312908).

Almost surely, 2^3938721 is an apocalyptic number.

It is an amenable number.

3938721 is a deficient number, since it is larger than the sum of its proper divisors (1312911).

3938721 is a wasteful number, since it uses less digits than its factorization.

3938721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1312910.

The product of its digits is 9072, while the sum is 33.

The square root of 3938721 is about 1984.6211225320. The cubic root of 3938721 is about 157.9253105298.

The spelling of 3938721 in words is "three million, nine hundred thirty-eight thousand, seven hundred twenty-one".