21816781443 has 12 divisors (see below), whose sum is σ = 31603949208. Its totient is φ = 14502603840.

The previous prime is 21816781423. The next prime is 21816781501. The reversal of 21816781443 is 34418761812.

It is not a de Polignac number, because 21816781443 - 2⁸ = 21816781187 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21816781423) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3489798 + ... + 3496043.

It is an arithmetic number, because the mean of its divisors is an integer number (2633662434).

Almost surely, 2^21816781443 is an apocalyptic number.

21816781443 is a deficient number, since it is larger than the sum of its proper divisors (9787167765).

21816781443 is a wasteful number, since it uses less digits than its factorization.

21816781443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6986194 (or 6986191 counting only the distinct ones).

The product of its digits is 258048, while the sum is 45.

The spelling of 21816781443 in words is "twenty-one billion, eight hundred sixteen million, seven hundred eighty-one thousand, four hundred forty-three".