21331404 has 48 divisors (see below), whose sum is σ = 55587840. Its totient is φ = 7074000.

The previous prime is 21331399. The next prime is 21331451. The reversal of 21331404 is 40413312.

It is a super-2 number, since 2×21331404² = 910057593222432, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28029 + ... + 28779.

It is an arithmetic number, because the mean of its divisors is an integer number (1158080).

Almost surely, 2^21331404 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21331404, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27793920).

21331404 is an abundant number, since it is smaller than the sum of its proper divisors (34256436).

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

21331404 is a wasteful number, since it uses less digits than its factorization.

21331404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1027 (or 1019 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21331404 is about 4618.5932923348. The cubic root of 21331404 is about 277.3361487068.

Adding to 21331404 its reverse (40413312), we get a palindrome (61744716).

The spelling of 21331404 in words is "twenty-one million, three hundred thirty-one thousand, four hundred four".