1243434205721 has 2 divisors, whose sum is σ = 1243434205722. Its totient is φ = 1243434205720.

The previous prime is 1243434205703. The next prime is 1243434205729. The reversal of 1243434205721 is 1275024343421.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 765073849225 + 478360356496 = 874685^2 + 691636^2 .

It is an emirp because it is prime and its reverse (1275024343421) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1243434205721 - 2²⁶ = 1243367096857 is a prime.

It is a super-2 number, since 2×1243434205721² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1243434205729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 621717102860 + 621717102861.

It is an arithmetic number, because the mean of its divisors is an integer number (621717102861).

Almost surely, 2^{1243434205721} is an apocalyptic number.

It is an amenable number.

1243434205721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1243434205721 is an equidigital number, since it uses as much as digits as its factorization.

1243434205721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 161280, while the sum is 38.

The spelling of 1243434205721 in words is "one trillion, two hundred forty-three billion, four hundred thirty-four million, two hundred five thousand, seven hundred twenty-one".