21681204 has 24 divisors (see below), whose sum is σ = 53252640. Its totient is φ = 6846624.

The previous prime is 21681193. The next prime is 21681211. The reversal of 21681204 is 40218612.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 47319 + ... + 47774.

It is an arithmetic number, because the mean of its divisors is an integer number (2218860).

Almost surely, 2^21681204 is an apocalyptic number.

It is an amenable number.

21681204 is an abundant number, since it is smaller than the sum of its proper divisors (31571436).

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

21681204 is a wasteful number, since it uses less digits than its factorization.

21681204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95119 (or 95117 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21681204 is about 4656.3079795048. The cubic root of 21681204 is about 278.8438894914.

Adding to 21681204 its reverse (40218612), we get a palindrome (61899816).

The spelling of 21681204 in words is "twenty-one million, six hundred eighty-one thousand, two hundred four".