21245420 has 96 divisors (see below), whose sum is σ = 55104000. Its totient is φ = 6858432.

The previous prime is 21245417. The next prime is 21245459. The reversal of 21245420 is 2454212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21245392 and 21245401.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 130259 + ... + 130421.

It is an arithmetic number, because the mean of its divisors is an integer number (574000).

Almost surely, 2^21245420 is an apocalyptic number.

21245420 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 21245420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27552000).

21245420 is an abundant number, since it is smaller than the sum of its proper divisors (33858580).

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

21245420 is a wasteful number, since it uses less digits than its factorization.

21245420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21245420 is about 4609.2754311280. The cubic root of 21245420 is about 276.9630120865.

Adding to 21245420 its reverse (2454212), we get a palindrome (23699632).

The spelling of 21245420 in words is "twenty-one million, two hundred forty-five thousand, four hundred twenty".