21499243 has 4 divisors (see below), whose sum is σ = 21578848. Its totient is φ = 21419640.

The previous prime is 21499223. The next prime is 21499249. The reversal of 21499243 is 34299412.

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 21499243 - 2¹³ = 21491051 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21499199 and 21499208.

It is not an unprimeable number, because it can be changed into a prime (21499249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39396 + ... + 39937.

It is an arithmetic number, because the mean of its divisors is an integer number (5394712).

Almost surely, 2^21499243 is an apocalyptic number.

21499243 is a deficient number, since it is larger than the sum of its proper divisors (79605).

21499243 is an equidigital number, since it uses as much as digits as its factorization.

21499243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79604.

The product of its digits is 15552, while the sum is 34.

The square root of 21499243 is about 4636.7276176200. The cubic root of 21499243 is about 278.0616247975.

The spelling of 21499243 in words is "twenty-one million, four hundred ninety-nine thousand, two hundred forty-three".