21222420 has 48 divisors (see below), whose sum is σ = 60879168. Its totient is φ = 5520640.

The previous prime is 21222401. The next prime is 21222433. The reversal of 21222420 is 2422212.

It is a super-2 number, since 2×21222420² = 900782221312800, which contains 22 as substring.

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 21222420.

It is a congruent number.

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, 1854 + ... + 6773.

It is an arithmetic number, because the mean of its divisors is an integer number (1268316).

Almost surely, 2^21222420 is an apocalyptic number.

21222420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21222420 is an abundant number, since it is smaller than the sum of its proper divisors (39656748).

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

21222420 is a wasteful number, since it uses less digits than its factorization.

21222420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8680 (or 8678 counting only the distinct ones).

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

The square root of 21222420 is about 4606.7797863584. The cubic root of 21222420 is about 276.8630305468.

Adding to 21222420 its reverse (2422212), we get a palindrome (23644632).

The spelling of 21222420 in words is "twenty-one million, two hundred twenty-two thousand, four hundred twenty".