12821991 has 32 divisors (see below), whose sum is σ = 21385728. Its totient is φ = 6652800.

The previous prime is 12821989. The next prime is 12822001. The reversal of 12821991 is 19912821.

It is not a de Polignac number, because 12821991 - 2¹ = 12821989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12821491) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17941 + ... + 18641.

It is an arithmetic number, because the mean of its divisors is an integer number (668304).

Almost surely, 2^12821991 is an apocalyptic number.

12821991 is a deficient number, since it is larger than the sum of its proper divisors (8563737).

12821991 is a wasteful number, since it uses less digits than its factorization.

12821991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 791.

The product of its digits is 2592, while the sum is 33.

The square root of 12821991 is about 3580.7807807795. The cubic root of 12821991 is about 234.0553050665.

The spelling of 12821991 in words is "twelve million, eight hundred twenty-one thousand, nine hundred ninety-one".