21243042 has 24 divisors (see below), whose sum is σ = 46325916. Its totient is φ = 7034976.

The previous prime is 21243023. The next prime is 21243049. The reversal of 21243042 is 24034212.

It can be written as a sum of positive squares in 2 ways, for example, as 20711601 + 531441 = 4551^2 + 729^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21243049) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 933 + ... + 6584.

Almost surely, 2^21243042 is an apocalyptic number.

21243042 is an abundant number, since it is smaller than the sum of its proper divisors (25082874).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21243042 is a wasteful number, since it uses less digits than its factorization.

21243042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7682 (or 7679 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21243042 is about 4609.0174657946. The cubic root of 21243042 is about 276.9526782103.

Adding to 21243042 its reverse (24034212), we get a palindrome (45277254).

The spelling of 21243042 in words is "twenty-one million, two hundred forty-three thousand, forty-two".