3945821 has 4 divisors (see below), whose sum is σ = 4304544. Its totient is φ = 3587100.

The previous prime is 3945803. The next prime is 3945841. The reversal of 3945821 is 1285493.

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 not a de Polignac number, because 3945821 - 2⁶ = 3945757 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 (3945841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 179345 + ... + 179366.

It is an arithmetic number, because the mean of its divisors is an integer number (1076136).

Almost surely, 2^3945821 is an apocalyptic number.

It is an amenable number.

3945821 is a deficient number, since it is larger than the sum of its proper divisors (358723).

3945821 is a wasteful number, since it uses less digits than its factorization.

3945821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 358722.

The product of its digits is 8640, while the sum is 32.

The square root of 3945821 is about 1986.4090716668. The cubic root of 3945821 is about 158.0201464456.

The spelling of 3945821 in words is "three million, nine hundred forty-five thousand, eight hundred twenty-one".