3921212221 has 4 divisors (see below), whose sum is σ = 3938041692. Its totient is φ = 3904382752.

The previous prime is 3921212213. The next prime is 3921212257. The reversal of 3921212221 is 1222121293.

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 668791321 + 3252420900 = 25861^2 + 57030^2 .

It is a cyclic number.

It is not a de Polignac number, because 3921212221 - 2³ = 3921212213 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 (3921212521) 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, 8414386 + ... + 8414851.

It is an arithmetic number, because the mean of its divisors is an integer number (984510423).

Almost surely, 2^3921212221 is an apocalyptic number.

It is an amenable number.

3921212221 is a deficient number, since it is larger than the sum of its proper divisors (16829471).

3921212221 is a wasteful number, since it uses less digits than its factorization.

3921212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16829470.

The product of its digits is 864, while the sum is 25.

The square root of 3921212221 is about 62619.5833665476. The cubic root of 3921212221 is about 1576.9095469812.

The spelling of 3921212221 in words is "three billion, nine hundred twenty-one million, two hundred twelve thousand, two hundred twenty-one".