21130042 has 4 divisors (see below), whose sum is σ = 31695066. Its totient is φ = 10565020.

The previous prime is 21130037. The next prime is 21130049. The reversal of 21130042 is 24003112.

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., 13682601 + 7447441 = 3699^2 + 2729^2 .

It is not an unprimeable number, because it can be changed into a prime (21130049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5282509 + ... + 5282512.

Almost surely, 2^21130042 is an apocalyptic number.

21130042 is a deficient number, since it is larger than the sum of its proper divisors (10565024).

21130042 is a wasteful number, since it uses less digits than its factorization.

21130042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10565023.

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

The square root of 21130042 is about 4596.7425422793. The cubic root of 21130042 is about 276.4607318990.

Adding to 21130042 its reverse (24003112), we get a palindrome (45133154).

The spelling of 21130042 in words is "twenty-one million, one hundred thirty thousand, forty-two".