191966821 has 2 divisors, whose sum is σ = 191966822. Its totient is φ = 191966820.

The previous prime is 191966813. The next prime is 191966833. The reversal of 191966821 is 128669191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 191517921 + 448900 = 13839^2 + 670^2 .

It is a cyclic number.

It is not a de Polignac number, because 191966821 - 2³ = 191966813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191966851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95983410 + 95983411.

It is an arithmetic number, because the mean of its divisors is an integer number (95983411).

Almost surely, 2^191966821 is an apocalyptic number.

It is an amenable number.

191966821 is a deficient number, since it is larger than the sum of its proper divisors (1).

191966821 is an equidigital number, since it uses as much as digits as its factorization.

191966821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 43.

The square root of 191966821 is about 13855.2091647871. The cubic root of 191966821 is about 576.8665953763.

The spelling of 191966821 in words is "one hundred ninety-one million, nine hundred sixty-six thousand, eight hundred twenty-one".