21121222021 has 4 divisors (see below), whose sum is σ = 21123155392. Its totient is φ = 21119288652.

The previous prime is 21121222009. The next prime is 21121222049. The reversal of 21121222021 is 12022212112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21121222021 - 2³¹ = 18973738373 is a prime.

It is a super-2 number, since 2×21121222021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121221986 and 21121222004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121222081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 950205 + ... + 972178.

It is an arithmetic number, because the mean of its divisors is an integer number (5280788848).

Almost surely, 2^21121222021 is an apocalyptic number.

It is an amenable number.

21121222021 is a deficient number, since it is larger than the sum of its proper divisors (1933371).

21121222021 is a wasteful number, since it uses less digits than its factorization.

21121222021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1933370.

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

Adding to 21121222021 its reverse (12022212112), we get a palindrome (33143434133).

Subtracting from 21121222021 its reverse (12022212112), we obtain a palindrome (9099009909).

The spelling of 21121222021 in words is "twenty-one billion, one hundred twenty-one million, two hundred twenty-two thousand, twenty-one".