21011222221 has 8 divisors (see below), whose sum is σ = 22979074464. Its totient is φ = 19052993520.

The previous prime is 21011222213. The next prime is 21011222279. The reversal of 21011222221 is 12222211012.

It is a happy number.

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

It is not a de Polignac number, because 21011222221 - 2³ = 21011222213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011222195 and 21011222204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011222201) 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, 2401315 + ... + 2410048.

It is an arithmetic number, because the mean of its divisors is an integer number (2872384308).

Almost surely, 2^21011222221 is an apocalyptic number.

It is an amenable number.

21011222221 is a deficient number, since it is larger than the sum of its proper divisors (1967852243).

21011222221 is a wasteful number, since it uses less digits than its factorization.

21011222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4811771.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21011222221 its reverse (12222211012), we get a palindrome (33233433233).

The spelling of 21011222221 in words is "twenty-one billion, eleven million, two hundred twenty-two thousand, two hundred twenty-one".