21001312221 has 8 divisors (see below), whose sum is σ = 28758553824. Its totient is φ = 13622472720.

The previous prime is 21001312193. The next prime is 21001312231. The reversal of 21001312221 is 12221310012.

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

It is not a de Polignac number, because 21001312221 - 2¹⁰ = 21001311197 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21001312221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001312231) 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, 94600395 + ... + 94600616.

It is an arithmetic number, because the mean of its divisors is an integer number (3594819228).

Almost surely, 2^21001312221 is an apocalyptic number.

It is an amenable number.

21001312221 is a deficient number, since it is larger than the sum of its proper divisors (7757241603).

21001312221 is a wasteful number, since it uses less digits than its factorization.

21001312221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189201051.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21001312221 its reverse (12221310012), we get a palindrome (33222622233).

The spelling of 21001312221 in words is "twenty-one billion, one million, three hundred twelve thousand, two hundred twenty-one".