21555330321 has 8 divisors (see below), whose sum is σ = 32846217664. Its totient is φ = 12317331600.

The previous prime is 21555330299. The next prime is 21555330343. The reversal of 21555330321 is 12303355512.

It is an interprime number because it is at equal distance from previous prime (21555330299) and next prime (21555330343).

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

It is not a de Polignac number, because 21555330321 - 2⁵ = 21555330289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555330361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 513222130 + ... + 513222171.

It is an arithmetic number, because the mean of its divisors is an integer number (4105777208).

Almost surely, 2^21555330321 is an apocalyptic number.

21555330321 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21555330321 is a deficient number, since it is larger than the sum of its proper divisors (11290887343).

21555330321 is a wasteful number, since it uses less digits than its factorization.

21555330321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1026444311.

The product of its (nonzero) digits is 13500, while the sum is 30.

Adding to 21555330321 its reverse (12303355512), we get a palindrome (33858685833).

The spelling of 21555330321 in words is "twenty-one billion, five hundred fifty-five million, three hundred thirty thousand, three hundred twenty-one".