21001321221 has 8 divisors (see below), whose sum is σ = 28002655200. Its totient is φ = 14000434032.

The previous prime is 21001321193. The next prime is 21001321241. The reversal of 21001321221 is 12212310012.

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

It is not a de Polignac number, because 21001321221 - 2⁶ = 21001321157 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21001321221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001321241) 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, 20251 + ... + 205943.

It is an arithmetic number, because the mean of its divisors is an integer number (3500331900).

Almost surely, 2^21001321221 is an apocalyptic number.

It is an amenable number.

21001321221 is a deficient number, since it is larger than the sum of its proper divisors (7001333979).

21001321221 is a wasteful number, since it uses less digits than its factorization.

21001321221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223395.

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

Adding to 21001321221 its reverse (12212310012), we get a palindrome (33213631233).

The spelling of 21001321221 in words is "twenty-one billion, one million, three hundred twenty-one thousand, two hundred twenty-one".