21042404 has 24 divisors (see below), whose sum is σ = 37529688. Its totient is φ = 10321920.

The previous prime is 21042383. The next prime is 21042407. The reversal of 21042404 is 40424012.

It can be written as a sum of positive squares in 4 ways, for example, as 2102500 + 18939904 = 1450^2 + 4352^2 .

It is not an unprimeable number, because it can be changed into a prime (21042407) 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, 74744 + ... + 75024.

It is an arithmetic number, because the mean of its divisors is an integer number (1563737).

Almost surely, 2^21042404 is an apocalyptic number.

It is an amenable number.

21042404 is a deficient number, since it is larger than the sum of its proper divisors (16487284).

21042404 is a wasteful number, since it uses less digits than its factorization.

21042404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 575 (or 573 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21042404 is about 4587.2000174398. The cubic root of 21042404 is about 276.0779902823.

Adding to 21042404 its reverse (40424012), we get a palindrome (61466416).

The spelling of 21042404 in words is "twenty-one million, forty-two thousand, four hundred four".