21404220 has 24 divisors (see below), whose sum is σ = 59931984. Its totient is φ = 5707776.

The previous prime is 21404213. The next prime is 21404263. The reversal of 21404220 is 2240412.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21404220.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 178309 + ... + 178428.

It is an arithmetic number, because the mean of its divisors is an integer number (2497166).

Almost surely, 2^21404220 is an apocalyptic number.

21404220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21404220 is an abundant number, since it is smaller than the sum of its proper divisors (38527764).

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

21404220 is a wasteful number, since it uses less digits than its factorization.

21404220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356749 (or 356747 counting only the distinct ones).

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

The square root of 21404220 is about 4626.4694962790. The cubic root of 21404220 is about 277.6513580589.

Adding to 21404220 its reverse (2240412), we get a palindrome (23644632).

The spelling of 21404220 in words is "twenty-one million, four hundred four thousand, two hundred twenty".