21042520 has 16 divisors (see below), whose sum is σ = 47345760. Its totient is φ = 8416992.

The previous prime is 21042491. The next prime is 21042533. The reversal of 21042520 is 2524012.

It is a junction number, because it is equal to n+sod(n) for n = 21042494 and 21042503.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262992 + ... + 263071.

It is an arithmetic number, because the mean of its divisors is an integer number (2959110).

Almost surely, 2^21042520 is an apocalyptic number.

21042520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21042520 is an abundant number, since it is smaller than the sum of its proper divisors (26303240).

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

21042520 is a wasteful number, since it uses less digits than its factorization.

21042520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 526074 (or 526070 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21042520 is about 4587.2126613010. The cubic root of 21042520 is about 276.0784975910.

Adding to 21042520 its reverse (2524012), we get a palindrome (23566532).

It can be divided in two parts, 2104 and 2520, that added together give a square (4624 = 68²).

The spelling of 21042520 in words is "twenty-one million, forty-two thousand, five hundred twenty".