3991001221 has 4 divisors (see below), whose sum is σ = 4019713600. Its totient is φ = 3962288844.

The previous prime is 3991001219. The next prime is 3991001233. The reversal of 3991001221 is 1221001993.

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 3991001221 - 2¹ = 3991001219 is a prime.

It is a super-3 number, since 3×3991001221³ (a number of 30 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 3991001221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991001291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14355981 + ... + 14356258.

It is an arithmetic number, because the mean of its divisors is an integer number (1004928400).

Almost surely, 2^3991001221 is an apocalyptic number.

It is an amenable number.

3991001221 is a deficient number, since it is larger than the sum of its proper divisors (28712379).

3991001221 is a wasteful number, since it uses less digits than its factorization.

3991001221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28712378.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 3991001221 is about 63174.3715520780. The cubic root of 3991001221 is about 1586.2097689091.

The spelling of 3991001221 in words is "three billion, nine hundred ninety-one million, one thousand, two hundred twenty-one".