3975821 has 4 divisors (see below), whose sum is σ = 3996000. Its totient is φ = 3955644.

The previous prime is 3975791. The next prime is 3975827. The reversal of 3975821 is 1285793.

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.

It is a cyclic number.

It is not a de Polignac number, because 3975821 - 2¹⁰ = 3974797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3975827) 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, 9791 + ... + 10188.

It is an arithmetic number, because the mean of its divisors is an integer number (999000).

Almost surely, 2^3975821 is an apocalyptic number.

It is an amenable number.

3975821 is a deficient number, since it is larger than the sum of its proper divisors (20179).

3975821 is a wasteful number, since it uses less digits than its factorization.

3975821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20178.

The product of its digits is 15120, while the sum is 35.

The square root of 3975821 is about 1993.9460875360. The cubic root of 3975821 is about 158.4196104729.

The spelling of 3975821 in words is "three million, nine hundred seventy-five thousand, eight hundred twenty-one".