21001021221 has 8 divisors (see below), whose sum is σ = 28002663360. Its totient is φ = 14000029952.

The previous prime is 21001021219. The next prime is 21001021229. The reversal of 21001021221 is 12212010012.

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

It is a cyclic number.

It is not a de Polignac number, because 21001021221 - 2¹ = 21001021219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001021197 and 21001021206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001021229) 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, 81660 + ... + 220613.

It is an arithmetic number, because the mean of its divisors is an integer number (3500332920).

Almost surely, 2^21001021221 is an apocalyptic number.

It is an amenable number.

21001021221 is a deficient number, since it is larger than the sum of its proper divisors (7001642139).

21001021221 is a wasteful number, since it uses less digits than its factorization.

21001021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325435.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001021221 its reverse (12212010012), we get a palindrome (33213031233).

The spelling of 21001021221 in words is "twenty-one billion, one million, twenty-one thousand, two hundred twenty-one".