21243575 has 6 divisors (see below), whose sum is σ = 26342064. Its totient is φ = 16994840.

The previous prime is 21243533. The next prime is 21243581. The reversal of 21243575 is 57534212.

It is a happy number.

It is not a de Polignac number, because 21243575 - 2¹² = 21239479 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 424847 + ... + 424896.

It is an arithmetic number, because the mean of its divisors is an integer number (4390344).

Almost surely, 2^21243575 is an apocalyptic number.

21243575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21243575 is a deficient number, since it is larger than the sum of its proper divisors (5098489).

21243575 is an equidigital number, since it uses as much as digits as its factorization.

21243575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 849753 (or 849748 counting only the distinct ones).

The product of its digits is 8400, while the sum is 29.

The square root of 21243575 is about 4609.0752868661. The cubic root of 21243575 is about 276.9549944910.

Adding to 21243575 its reverse (57534212), we get a palindrome (78777787).

The spelling of 21243575 in words is "twenty-one million, two hundred forty-three thousand, five hundred seventy-five".