21407220 has 96 divisors (see below), whose sum is σ = 68947200. Its totient is φ = 5507712.

The previous prime is 21407213. The next prime is 21407257. The reversal of 21407220 is 2270412.

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

It is a junction number, because it is equal to n+sod(n) for n = 21407193 and 21407202.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 14977 + ... + 16343.

It is an arithmetic number, because the mean of its divisors is an integer number (718200).

Almost surely, 2^21407220 is an apocalyptic number.

21407220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21407220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34473600).

21407220 is an abundant number, since it is smaller than the sum of its proper divisors (47539980).

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

21407220 is a wasteful number, since it uses less digits than its factorization.

21407220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1414 (or 1406 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 21407220 is about 4626.7937062290. The cubic root of 21407220 is about 277.6643292575.

Adding to 21407220 its reverse (2270412), we get a palindrome (23677632).

The spelling of 21407220 in words is "twenty-one million, four hundred seven thousand, two hundred twenty".