21550404 has 12 divisors (see below), whose sum is σ = 50284304. Its totient is φ = 7183464.

The previous prime is 21550387. The next prime is 21550409. The reversal of 21550404 is 40405512.

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 (21550409) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 897922 + ... + 897945.

Almost surely, 2^21550404 is an apocalyptic number.

It is an amenable number.

21550404 is an abundant number, since it is smaller than the sum of its proper divisors (28733900).

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

21550404 is a wasteful number, since it uses less digits than its factorization.

21550404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1795874 (or 1795872 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21550404 is about 4642.2412690424. The cubic root of 21550404 is about 278.2820145942.

Adding to 21550404 its reverse (40405512), we get a palindrome (61955916).

The spelling of 21550404 in words is "twenty-one million, five hundred fifty thousand, four hundred four".