21123021221 has 16 divisors (see below), whose sum is σ = 23252476800. Its totient is φ = 19099162368.

The previous prime is 21123021217. The next prime is 21123021253. The reversal of 21123021221 is 12212032112.

It is not a de Polignac number, because 21123021221 - 2² = 21123021217 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21123021221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123021121) 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 15 ways as a sum of consecutive naturals, for example, 146825 + ... + 252593.

It is an arithmetic number, because the mean of its divisors is an integer number (1453279800).

Almost surely, 2^21123021221 is an apocalyptic number.

It is an amenable number.

21123021221 is a deficient number, since it is larger than the sum of its proper divisors (2129455579).

21123021221 is a wasteful number, since it uses less digits than its factorization.

21123021221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106268.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21123021221 its reverse (12212032112), we get a palindrome (33335053333).

The spelling of 21123021221 in words is "twenty-one billion, one hundred twenty-three million, twenty-one thousand, two hundred twenty-one".