21221222021 has 16 divisors (see below), whose sum is σ = 23003543808. Its totient is φ = 19524489600.

The previous prime is 21221221997. The next prime is 21221222023. The reversal of 21221222021 is 12022212212.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21221222021 - 2¹⁰ = 21221220997 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 (21221222023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91526 + ... + 225431.

It is an arithmetic number, because the mean of its divisors is an integer number (1437721488).

Almost surely, 2^21221222021 is an apocalyptic number.

It is an amenable number.

21221222021 is a deficient number, since it is larger than the sum of its proper divisors (1782321787).

21221222021 is a wasteful number, since it uses less digits than its factorization.

21221222021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317092.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21221222021 its reverse (12022212212), we get a palindrome (33243434233).

The spelling of 21221222021 in words is "twenty-one billion, two hundred twenty-one million, two hundred twenty-two thousand, twenty-one".