12191821 has 2 divisors, whose sum is σ = 12191822. Its totient is φ = 12191820.

The previous prime is 12191813. The next prime is 12191831. The reversal of 12191821 is 12819121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10465225 + 1726596 = 3235^2 + 1314^2 .

It is a cyclic number.

It is not a de Polignac number, because 12191821 - 2³ = 12191813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (12191831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6095910 + 6095911.

It is an arithmetic number, because the mean of its divisors is an integer number (6095911).

Almost surely, 2^12191821 is an apocalyptic number.

It is an amenable number.

12191821 is a deficient number, since it is larger than the sum of its proper divisors (1).

12191821 is an equidigital number, since it uses as much as digits as its factorization.

12191821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 25.

The square root of 12191821 is about 3491.6788225723. The cubic root of 12191821 is about 230.1562957820.

The spelling of 12191821 in words is "twelve million, one hundred ninety-one thousand, eight hundred twenty-one".