1243854135221 has 2 divisors, whose sum is σ = 1243854135222. Its totient is φ = 1243854135220.

The previous prime is 1243854135193. The next prime is 1243854135281. The reversal of 1243854135221 is 1225314583421.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1205573256196 + 38280879025 = 1097986^2 + 195655^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1243854135221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1243854135281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 621927067610 + 621927067611.

It is an arithmetic number, because the mean of its divisors is an integer number (621927067611).

Almost surely, 2^{1243854135221} is an apocalyptic number.

It is an amenable number.

1243854135221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1243854135221 is an equidigital number, since it uses as much as digits as its factorization.

1243854135221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 230400, while the sum is 41.

The spelling of 1243854135221 in words is "one trillion, two hundred forty-three billion, eight hundred fifty-four million, one hundred thirty-five thousand, two hundred twenty-one".