191212421 has 2 divisors, whose sum is σ = 191212422. Its totient is φ = 191212420.

The previous prime is 191212391. The next prime is 191212429. The reversal of 191212421 is 124212191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 191130625 + 81796 = 13825^2 + 286^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191212421 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191212429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95606210 + 95606211.

It is an arithmetic number, because the mean of its divisors is an integer number (95606211).

Almost surely, 2^191212421 is an apocalyptic number.

It is an amenable number.

191212421 is a deficient number, since it is larger than the sum of its proper divisors (1).

191212421 is an equidigital number, since it uses as much as digits as its factorization.

191212421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 288, while the sum is 23.

The square root of 191212421 is about 13827.9579475785. The cubic root of 191212421 is about 576.1099377427.

The spelling of 191212421 in words is "one hundred ninety-one million, two hundred twelve thousand, four hundred twenty-one".