21545225 has 12 divisors (see below), whose sum is σ = 28771596. Its totient is φ = 15910080.

The previous prime is 21545203. The next prime is 21545233. The reversal of 21545225 is 52254512.

It can be written as a sum of positive squares in 6 ways, for example, as 5053504 + 16491721 = 2248^2 + 4061^2 .

It is not a de Polignac number, because 21545225 - 2¹² = 21541129 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21545194 and 21545203.

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, 32822 + ... + 33471.

It is an arithmetic number, because the mean of its divisors is an integer number (2397633).

Almost surely, 2^21545225 is an apocalyptic number.

21545225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21545225 is a deficient number, since it is larger than the sum of its proper divisors (7226371).

21545225 is a wasteful number, since it uses less digits than its factorization.

21545225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66316 (or 66311 counting only the distinct ones).

The product of its digits is 4000, while the sum is 26.

The square root of 21545225 is about 4641.6834230697. The cubic root of 21545225 is about 278.2597205339.

Adding to 21545225 its reverse (52254512), we get a palindrome (73799737).

The spelling of 21545225 in words is "twenty-one million, five hundred forty-five thousand, two hundred twenty-five".