243835578876821 has 4 divisors (see below), whose sum is σ = 243835619902092. Its totient is φ = 243835537851552.

The previous prime is 243835578876809. The next prime is 243835578876949. The reversal of 243835578876821 is 128678875538342.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 237271663140625 + 6563915736196 = 15403625^2 + 2562014^2 .

It is a cyclic number.

It is not a de Polignac number, because 243835578876821 - 2²² = 243835574682517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243838578876821) 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, 9696086 + ... + 24118151.

It is an arithmetic number, because the mean of its divisors is an integer number (60958904975523).

Almost surely, 2^{243835578876821} is an apocalyptic number.

It is an amenable number.

243835578876821 is a deficient number, since it is larger than the sum of its proper divisors (41025271).

243835578876821 is an equidigital number, since it uses as much as digits as its factorization.

243835578876821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41025270.

The product of its digits is 4335206400, while the sum is 77.

The spelling of 243835578876821 in words is "two hundred forty-three trillion, eight hundred thirty-five billion, five hundred seventy-eight million, eight hundred seventy-six thousand, eight hundred twenty-one".