21010243 has 4 divisors (see below), whose sum is σ = 21035728. Its totient is φ = 20984760.

The previous prime is 21010237. The next prime is 21010259. The reversal of 21010243 is 34201012.

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 21010243 - 2⁹ = 21009731 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21010543) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11463 + ... + 13168.

It is an arithmetic number, because the mean of its divisors is an integer number (5258932).

Almost surely, 2^21010243 is an apocalyptic number.

21010243 is a deficient number, since it is larger than the sum of its proper divisors (25485).

21010243 is an equidigital number, since it uses as much as digits as its factorization.

21010243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25484.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21010243 is about 4583.6931616329. The cubic root of 21010243 is about 275.9372669507.

Adding to 21010243 its reverse (34201012), we get a palindrome (55211255).

The spelling of 21010243 in words is "twenty-one million, ten thousand, two hundred forty-three".