21505004 has 6 divisors (see below), whose sum is σ = 37633764. Its totient is φ = 10752500.

The previous prime is 21504971. The next prime is 21505007. The reversal of 21505004 is 40050512.

It is not an unprimeable number, because it can be changed into a prime (21505007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2688122 + ... + 2688129.

It is an arithmetic number, because the mean of its divisors is an integer number (6272294).

Almost surely, 2^21505004 is an apocalyptic number.

It is an amenable number.

21505004 is a deficient number, since it is larger than the sum of its proper divisors (16128760).

21505004 is a wasteful number, since it uses less digits than its factorization.

21505004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5376255 (or 5376253 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 17.

The square root of 21505004 is about 4637.3488115517. The cubic root of 21505004 is about 278.0864593147.

Adding to 21505004 its reverse (40050512), we get a palindrome (61555516).

The spelling of 21505004 in words is "twenty-one million, five hundred five thousand, four".