21558225 has 24 divisors (see below), whose sum is σ = 38386432. Its totient is φ = 10612800.

The previous prime is 21558221. The next prime is 21558233. The reversal of 21558225 is 52285512.

It is not a de Polignac number, because 21558225 - 2² = 21558221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21558192 and 21558201.

It is not an unprimeable number, because it can be changed into a prime (21558221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10081 + ... + 12030.

Almost surely, 2^21558225 is an apocalyptic number.

21558225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21558225 is a deficient number, since it is larger than the sum of its proper divisors (16828207).

21558225 is a wasteful number, since it uses less digits than its factorization.

21558225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22137 (or 22132 counting only the distinct ones).

The product of its digits is 8000, while the sum is 30.

The square root of 21558225 is about 4643.0835659075. The cubic root of 21558225 is about 278.3156749129.

The spelling of 21558225 in words is "twenty-one million, five hundred fifty-eight thousand, two hundred twenty-five".