21105545225 has 6 divisors (see below), whose sum is σ = 26170876110. Its totient is φ = 16884436160.

The previous prime is 21105545221. The next prime is 21105545243. The reversal of 21105545225 is 52254550112.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 3854298889 + 17251246336 = 62083^2 + 131344^2 .

It is not a de Polignac number, because 21105545225 - 2² = 21105545221 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21105545191 and 21105545200.

It is not an unprimeable number, because it can be changed into a prime (21105545221) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 422110880 + ... + 422110929.

It is an arithmetic number, because the mean of its divisors is an integer number (4361812685).

Almost surely, 2^21105545225 is an apocalyptic number.

21105545225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21105545225 is a deficient number, since it is larger than the sum of its proper divisors (5065330885).

21105545225 is an equidigital number, since it uses as much as digits as its factorization.

21105545225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844221819 (or 844221814 counting only the distinct ones).

The product of its (nonzero) digits is 20000, while the sum is 32.

The spelling of 21105545225 in words is "twenty-one billion, one hundred five million, five hundred forty-five thousand, two hundred twenty-five".