21011001221 has 8 divisors (see below), whose sum is σ = 24113045760. Its totient is φ = 17934074928.

The previous prime is 21011001217. The next prime is 21011001251. The reversal of 21011001221 is 12210011012.

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

It is not a de Polignac number, because 21011001221 - 2² = 21011001217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011001251) 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, 6277766 + ... + 6281111.

It is an arithmetic number, because the mean of its divisors is an integer number (3014130720).

Almost surely, 2^21011001221 is an apocalyptic number.

It is an amenable number.

21011001221 is a deficient number, since it is larger than the sum of its proper divisors (3102044539).

21011001221 is a wasteful number, since it uses less digits than its factorization.

21011001221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12559123.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21011001221 its reverse (12210011012), we get a palindrome (33221012233).

The spelling of 21011001221 in words is "twenty-one billion, eleven million, one thousand, two hundred twenty-one".