21909865818 has 16 divisors (see below), whose sum is σ = 43871970240. Its totient is φ = 7294582176.

The previous prime is 21909865801. The next prime is 21909865823. The reversal of 21909865818 is 81856890912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2171155 + ... + 2181222.

It is an arithmetic number, because the mean of its divisors is an integer number (2741998140).

Almost surely, 2^21909865818 is an apocalyptic number.

21909865818 is an abundant number, since it is smaller than the sum of its proper divisors (21962104422).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21909865818 is a wasteful number, since it uses less digits than its factorization.

21909865818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4353221.

The product of its (nonzero) digits is 2488320, while the sum is 57.

The spelling of 21909865818 in words is "twenty-one billion, nine hundred nine million, eight hundred sixty-five thousand, eight hundred eighteen".