21261247 has 24 divisors (see below), whose sum is σ = 26717040. Its totient is φ = 16813440.

The previous prime is 21261241. The next prime is 21261259. The reversal of 21261247 is 74216212.

It is not a de Polignac number, because 21261247 - 2³ = 21261239 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261241) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 37893 + ... + 38449.

It is an arithmetic number, because the mean of its divisors is an integer number (1113210).

Almost surely, 2^21261247 is an apocalyptic number.

21261247 is a deficient number, since it is larger than the sum of its proper divisors (5455793).

21261247 is a wasteful number, since it uses less digits than its factorization.

21261247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 631 (or 624 counting only the distinct ones).

The product of its digits is 1344, while the sum is 25.

The square root of 21261247 is about 4610.9919757033. The cubic root of 21261247 is about 277.0317705222.

Adding to 21261247 its reverse (74216212), we get a palindrome (95477459).

The spelling of 21261247 in words is "twenty-one million, two hundred sixty-one thousand, two hundred forty-seven".