21135247 has 8 divisors (see below), whose sum is σ = 24203552. Its totient is φ = 18079200.

The previous prime is 21135227. The next prime is 21135259. The reversal of 21135247 is 74253112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21135247 - 2⁷ = 21135119 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21135227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 997 + ... + 6577.

It is an arithmetic number, because the mean of its divisors is an integer number (3025444).

Almost surely, 2^21135247 is an apocalyptic number.

21135247 is a deficient number, since it is larger than the sum of its proper divisors (3068305).

21135247 is an equidigital number, since it uses as much as digits as its factorization.

21135247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6129.

The product of its digits is 1680, while the sum is 25.

The square root of 21135247 is about 4597.3086692107. The cubic root of 21135247 is about 276.4834303863.

Adding to 21135247 its reverse (74253112), we get a palindrome (95388359).

The spelling of 21135247 in words is "twenty-one million, one hundred thirty-five thousand, two hundred forty-seven".