21156225 has 48 divisors (see below), whose sum is σ = 36961920. Its totient is φ = 10662400.

The previous prime is 21156181. The next prime is 21156227. The reversal of 21156225 is 52265112.

It is a happy number.

It is not a de Polignac number, because 21156225 - 2¹⁰ = 21155201 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21156195 and 21156204.

It is not an unprimeable number, because it can be changed into a prime (21156227) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 154357 + ... + 154493.

It is an arithmetic number, because the mean of its divisors is an integer number (770040).

Almost surely, 2^21156225 is an apocalyptic number.

21156225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21156225 is a deficient number, since it is larger than the sum of its proper divisors (15805695).

21156225 is a wasteful number, since it uses less digits than its factorization.

21156225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250 (or 245 counting only the distinct ones).

The product of its digits is 1200, while the sum is 24.

The square root of 21156225 is about 4599.5896556106. The cubic root of 21156225 is about 276.5748755993.

The spelling of 21156225 in words is "twenty-one million, one hundred fifty-six thousand, two hundred twenty-five".