21087204 has 12 divisors (see below), whose sum is σ = 49203504. Its totient is φ = 7029064.

The previous prime is 21087203. The next prime is 21087211. The reversal of 21087204 is 40278012.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21087203) 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 in 3 ways as a sum of consecutive naturals, for example, 878622 + ... + 878645.

It is an arithmetic number, because the mean of its divisors is an integer number (4100292).

Almost surely, 2^21087204 is an apocalyptic number.

It is an amenable number.

21087204 is an abundant number, since it is smaller than the sum of its proper divisors (28116300).

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

21087204 is a wasteful number, since it uses less digits than its factorization.

21087204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1757274 (or 1757272 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21087204 is about 4592.0805742060. The cubic root of 21087204 is about 276.2737779059.

The spelling of 21087204 in words is "twenty-one million, eighty-seven thousand, two hundred four".