21225247 has 4 divisors (see below), whose sum is σ = 21676896. Its totient is φ = 20773600.

The previous prime is 21225233. The next prime is 21225263. The reversal of 21225247 is 74252212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21225247 - 2⁷ = 21225119 is a prime.

It is a super-2 number, since 2×21225247² = 901022220422018, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225277) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 225754 + ... + 225847.

It is an arithmetic number, because the mean of its divisors is an integer number (5419224).

Almost surely, 2^21225247 is an apocalyptic number.

21225247 is a deficient number, since it is larger than the sum of its proper divisors (451649).

21225247 is an equidigital number, since it uses as much as digits as its factorization.

21225247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 451648.

The product of its digits is 2240, while the sum is 25.

The square root of 21225247 is about 4607.0866065226. The cubic root of 21225247 is about 276.8753234747.

Adding to 21225247 its reverse (74252212), we get a palindrome (95477459).

The spelling of 21225247 in words is "twenty-one million, two hundred twenty-five thousand, two hundred forty-seven".