21087065818 has 40 divisors (see below), whose sum is σ = 39738761748. Its totient is φ = 8342111232.

The previous prime is 21087065809. The next prime is 21087065819. The reversal of 21087065818 is 81856078012.

It can be written as a sum of positive squares in 2 ways, for example, as 21079264969 + 7800849 = 145187^2 + 2793^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21087065819) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 106471 + ... + 231322.

Almost surely, 2^21087065818 is an apocalyptic number.

21087065818 is a deficient number, since it is larger than the sum of its proper divisors (18651695930).

21087065818 is an equidigital number, since it uses as much as digits as its factorization.

21087065818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 337836 (or 337815 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 46.

The spelling of 21087065818 in words is "twenty-one billion, eighty-seven million, sixty-five thousand, eight hundred eighteen".