243900721 has 4 divisors (see below), whose sum is σ = 244390000. Its totient is φ = 243411444.

The previous prime is 243900667. The next prime is 243900733. The reversal of 243900721 is 127009342.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 243900721 - 2⁷ = 243900593 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 243900721.

It is not an unprimeable number, because it can be changed into a prime (243900421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 243891 + ... + 244888.

It is an arithmetic number, because the mean of its divisors is an integer number (61097500).

Almost surely, 2^243900721 is an apocalyptic number.

It is an amenable number.

243900721 is a deficient number, since it is larger than the sum of its proper divisors (489279).

243900721 is an equidigital number, since it uses as much as digits as its factorization.

243900721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 489278.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 243900721 is about 15617.3211851457. The cubic root of 243900721 is about 624.7952148282.

The spelling of 243900721 in words is "two hundred forty-three million, nine hundred thousand, seven hundred twenty-one".