21042530 has 16 divisors (see below), whose sum is σ = 38168064. Its totient is φ = 8352240.

The previous prime is 21042491. The next prime is 21042533. The reversal of 21042530 is 3524012.

It is a junction number, because it is equal to n+sod(n) for n = 21042499 and 21042508.

It is not an unprimeable number, because it can be changed into a prime (21042533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6722 + ... + 9341.

It is an arithmetic number, because the mean of its divisors is an integer number (2385504).

Almost surely, 2^21042530 is an apocalyptic number.

21042530 is a deficient number, since it is larger than the sum of its proper divisors (17125534).

21042530 is a wasteful number, since it uses less digits than its factorization.

21042530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16201.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21042530 is about 4587.2137512874. The cubic root of 21042530 is about 276.0785413245.

Adding to 21042530 its reverse (3524012), we get a palindrome (24566542).

The spelling of 21042530 in words is "twenty-one million, forty-two thousand, five hundred thirty".