21243020042 has 4 divisors (see below), whose sum is σ = 31864530066. Its totient is φ = 10621510020.

The previous prime is 21243020027. The next prime is 21243020059. The reversal of 21243020042 is 24002034212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20354443561 + 888576481 = 142669^2 + 29809^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21243019996 and 21243020023.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5310755009 + ... + 5310755012.

Almost surely, 2^21243020042 is an apocalyptic number.

21243020042 is a deficient number, since it is larger than the sum of its proper divisors (10621510024).

21243020042 is a wasteful number, since it uses less digits than its factorization.

21243020042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10621510023.

The product of its (nonzero) digits is 768, while the sum is 20.

Adding to 21243020042 its reverse (24002034212), we get a palindrome (45245054254).

The spelling of 21243020042 in words is "twenty-one billion, two hundred forty-three million, twenty thousand, forty-two".