243123721 has 2 divisors, whose sum is σ = 243123722. Its totient is φ = 243123720.

The previous prime is 243123701. The next prime is 243123761. The reversal of 243123721 is 127321342.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 121881600 + 121242121 = 11040^2 + 11011^2 .

It is a cyclic number.

It is not a de Polignac number, because 243123721 - 2¹³ = 243115529 is a prime.

It is not a weakly prime, because it can be changed into another prime (243123701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121561860 + 121561861.

It is an arithmetic number, because the mean of its divisors is an integer number (121561861).

Almost surely, 2^243123721 is an apocalyptic number.

It is an amenable number.

243123721 is a deficient number, since it is larger than the sum of its proper divisors (1).

243123721 is an equidigital number, since it uses as much as digits as its factorization.

243123721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 25.

The square root of 243123721 is about 15592.4251160620. The cubic root of 243123721 is about 624.1310343177.

The spelling of 243123721 in words is "two hundred forty-three million, one hundred twenty-three thousand, seven hundred twenty-one".