21355505999 has 8 divisors (see below), whose sum is σ = 21616761600. Its totient is φ = 21094344856.

The previous prime is 21355505987. The next prime is 21355506031. The reversal of 21355505999 is 99950555312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21355505999 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21355505999.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355505909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 502394 + ... + 543240.

It is an arithmetic number, because the mean of its divisors is an integer number (2702095200).

Almost surely, 2^21355505999 is an apocalyptic number.

21355505999 is a deficient number, since it is larger than the sum of its proper divisors (261255601).

21355505999 is an equidigital number, since it uses as much as digits as its factorization.

21355505999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47229.

The product of its (nonzero) digits is 2733750, while the sum is 53.

The spelling of 21355505999 in words is "twenty-one billion, three hundred fifty-five million, five hundred five thousand, nine hundred ninety-nine".