21491105225 has 12 divisors (see below), whose sum is σ = 26681936220. Its totient is φ = 17171616000.

The previous prime is 21491105191. The next prime is 21491105231. The reversal of 21491105225 is 52250119412.

It can be written as a sum of positive squares in 6 ways, for example, as 2148971449 + 19342133776 = 46357^2 + 139076^2 .

It is not a de Polignac number, because 21491105225 - 2⁶ = 21491105161 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21491105191 and 21491105200.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 511076 + ... + 551525.

It is an arithmetic number, because the mean of its divisors is an integer number (2223494685).

Almost surely, 2^21491105225 is an apocalyptic number.

21491105225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21491105225 is a deficient number, since it is larger than the sum of its proper divisors (5190830995).

21491105225 is a wasteful number, since it uses less digits than its factorization.

21491105225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1063420 (or 1063415 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 32.

The spelling of 21491105225 in words is "twenty-one billion, four hundred ninety-one million, one hundred five thousand, two hundred twenty-five".