21815800243 has 2 divisors, whose sum is σ = 21815800244. Its totient is φ = 21815800242.

The previous prime is 21815800211. The next prime is 21815800297. The reversal of 21815800243 is 34200851812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21815800243 - 2⁵ = 21815800211 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21815800199 and 21815800208.

It is not a weakly prime, because it can be changed into another prime (21815840243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10907900121 + 10907900122.

It is an arithmetic number, because the mean of its divisors is an integer number (10907900122).

Almost surely, 2^21815800243 is an apocalyptic number.

21815800243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21815800243 is an equidigital number, since it uses as much as digits as its factorization.

21815800243 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15360, while the sum is 34.

The spelling of 21815800243 in words is "twenty-one billion, eight hundred fifteen million, eight hundred thousand, two hundred forty-three".