21720355038518 has 16 divisors (see below), whose sum is σ = 32601370475520. Its totient is φ = 10853231882856.

The previous prime is 21720355038509. The next prime is 21720355038523. The reversal of 21720355038518 is 81583055302712.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 219084563 + ... + 219183681.

It is an arithmetic number, because the mean of its divisors is an integer number (2037585654720).

Almost surely, 2^{21720355038518} is an apocalyptic number.

21720355038518 is a deficient number, since it is larger than the sum of its proper divisors (10881015437002).

21720355038518 is a wasteful number, since it uses less digits than its factorization.

21720355038518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168091.

The product of its (nonzero) digits is 2016000, while the sum is 50.

The spelling of 21720355038518 in words is "twenty-one trillion, seven hundred twenty billion, three hundred fifty-five million, thirty-eight thousand, five hundred eighteen".