21921225 has 12 divisors (see below), whose sum is σ = 36243216. Its totient is φ = 11691280.

The previous prime is 21921191. The next prime is 21921227. The reversal of 21921225 is 52212912.

It is not a de Polignac number, because 21921225 - 2¹⁵ = 21888457 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21921195 and 21921204.

It is not an unprimeable number, because it can be changed into a prime (21921227) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 146067 + ... + 146216.

It is an arithmetic number, because the mean of its divisors is an integer number (3020268).

Almost surely, 2^21921225 is an apocalyptic number.

21921225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21921225 is a deficient number, since it is larger than the sum of its proper divisors (14321991).

21921225 is a wasteful number, since it uses less digits than its factorization.

21921225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 292296 (or 292291 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 21921225 is about 4682.0107859765. The cubic root of 21921225 is about 279.8690927185.

The spelling of 21921225 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred twenty-five".