1991203321 has 4 divisors (see below), whose sum is σ = 1999749492. Its totient is φ = 1982657152.

The previous prime is 1991203303. The next prime is 1991203337. The reversal of 1991203321 is 1233021991.

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 689797696 + 1301405625 = 26264^2 + 36075^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991203321 - 2¹⁵ = 1991170553 is a prime.

It is a super-2 number, since 2×1991203321² = 7929781331122858082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991203301) 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, 4272736 + ... + 4273201.

It is an arithmetic number, because the mean of its divisors is an integer number (499937373).

Almost surely, 2^1991203321 is an apocalyptic number.

It is an amenable number.

1991203321 is a deficient number, since it is larger than the sum of its proper divisors (8546171).

1991203321 is an equidigital number, since it uses as much as digits as its factorization.

1991203321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8546170.

The product of its (nonzero) digits is 2916, while the sum is 31.

The square root of 1991203321 is about 44622.9013063920. The cubic root of 1991203321 is about 1258.0711482327.

The spelling of 1991203321 in words is "one billion, nine hundred ninety-one million, two hundred three thousand, three hundred twenty-one".