21123521221 has 4 divisors (see below), whose sum is σ = 23043841344. Its totient is φ = 19203201100.

The previous prime is 21123521203. The next prime is 21123521227. The reversal of 21123521221 is 12212532112.

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 21123521221 - 2⁵ = 21123521189 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21123521192 and 21123521201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123521227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 960160045 + ... + 960160066.

It is an arithmetic number, because the mean of its divisors is an integer number (5760960336).

Almost surely, 2^21123521221 is an apocalyptic number.

It is an amenable number.

21123521221 is a deficient number, since it is larger than the sum of its proper divisors (1920320123).

21123521221 is a wasteful number, since it uses less digits than its factorization.

21123521221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1920320122.

The product of its digits is 480, while the sum is 22.

The spelling of 21123521221 in words is "twenty-one billion, one hundred twenty-three million, five hundred twenty-one thousand, two hundred twenty-one".