21405521121 has 32 divisors (see below), whose sum is σ = 29851597440. Its totient is φ = 13630656000.

The previous prime is 21405521107. The next prime is 21405521171. The reversal of 21405521121 is 12112550412.

It is a happy number.

It is not a de Polignac number, because 21405521121 - 2⁷ = 21405520993 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21405521091 and 21405521100.

It is not an unprimeable number, because it can be changed into a prime (21405521171) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3314946 + ... + 3321396.

It is an arithmetic number, because the mean of its divisors is an integer number (932862420).

Almost surely, 2^21405521121 is an apocalyptic number.

It is an amenable number.

21405521121 is a deficient number, since it is larger than the sum of its proper divisors (8446076319).

21405521121 is a wasteful number, since it uses less digits than its factorization.

21405521121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7057.

The product of its (nonzero) digits is 800, while the sum is 24.

The spelling of 21405521121 in words is "twenty-one billion, four hundred five million, five hundred twenty-one thousand, one hundred twenty-one".