21731275 has 6 divisors (see below), whose sum is σ = 26946812. Its totient is φ = 17385000.

The previous prime is 21731273. The next prime is 21731291. The reversal of 21731275 is 57213712.

It is not a de Polignac number, because 21731275 - 2¹ = 21731273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21731273) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 434601 + ... + 434650.

Almost surely, 2^21731275 is an apocalyptic number.

21731275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21731275 is a deficient number, since it is larger than the sum of its proper divisors (5215537).

21731275 is an equidigital number, since it uses as much as digits as its factorization.

21731275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 869261 (or 869256 counting only the distinct ones).

The product of its digits is 2940, while the sum is 28.

The square root of 21731275 is about 4661.6815635562. The cubic root of 21731275 is about 279.0583803184.

Adding to 21731275 its reverse (57213712), we get a palindrome (78944987).

The spelling of 21731275 in words is "twenty-one million, seven hundred thirty-one thousand, two hundred seventy-five".