12921991 has 6 divisors (see below), whose sum is σ = 13282080. Its totient is φ = 12571416.

The previous prime is 12921967. The next prime is 12922001. The reversal of 12921991 is 19912921.

It is not a de Polignac number, because 12921991 - 2⁷ = 12921863 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 (12921901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3351 + ... + 6088.

It is an arithmetic number, because the mean of its divisors is an integer number (2213680).

Almost surely, 2^12921991 is an apocalyptic number.

12921991 is a deficient number, since it is larger than the sum of its proper divisors (360089).

12921991 is an frugal number, since it uses more digits than its factorization.

12921991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9513 (or 9476 counting only the distinct ones).

The product of its digits is 2916, while the sum is 34.

The square root of 12921991 is about 3594.7170959618. The cubic root of 12921991 is about 234.6622036732.

The spelling of 12921991 in words is "twelve million, nine hundred twenty-one thousand, nine hundred ninety-one".