243199721 has 2 divisors, whose sum is σ = 243199722. Its totient is φ = 243199720.

The previous prime is 243199717. The next prime is 243199763. The reversal of 243199721 is 127991342.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 229219600 + 13980121 = 15140^2 + 3739^2 .

It is a cyclic number.

It is not a de Polignac number, because 243199721 - 2² = 243199717 is a prime.

It is a super-2 number, since 2×243199721² = 118292208588955682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (243199321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121599860 + 121599861.

It is an arithmetic number, because the mean of its divisors is an integer number (121599861).

Almost surely, 2^243199721 is an apocalyptic number.

It is an amenable number.

243199721 is a deficient number, since it is larger than the sum of its proper divisors (1).

243199721 is an equidigital number, since it uses as much as digits as its factorization.

243199721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 38.

The square root of 243199721 is about 15594.8620064430. The cubic root of 243199721 is about 624.1960615896.

The spelling of 243199721 in words is "two hundred forty-three million, one hundred ninety-nine thousand, seven hundred twenty-one".