21220404 has 12 divisors (see below), whose sum is σ = 49514304. Its totient is φ = 7073464.

The previous prime is 21220393. The next prime is 21220417. The reversal of 21220404 is 40402212.

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

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 3 ways as a sum of consecutive naturals, for example, 884172 + ... + 884195.

It is an arithmetic number, because the mean of its divisors is an integer number (4126192).

Almost surely, 2^21220404 is an apocalyptic number.

It is an amenable number.

21220404 is an abundant number, since it is smaller than the sum of its proper divisors (28293900).

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

21220404 is a wasteful number, since it uses less digits than its factorization.

21220404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1768374 (or 1768372 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21220404 is about 4606.5609732207. The cubic root of 21220404 is about 276.8542635048.

Adding to 21220404 its reverse (40402212), we get a palindrome (61622616).

The spelling of 21220404 in words is "twenty-one million, two hundred twenty thousand, four hundred four".