21220472 has 64 divisors (see below), whose sum is σ = 49620480. Its totient is φ = 8284032.

The previous prime is 21220429. The next prime is 21220477. The reversal of 21220472 is 27402212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220477) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74843 + ... + 75125.

It is an arithmetic number, because the mean of its divisors is an integer number (775320).

Almost surely, 2^21220472 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 21220472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24810240).

21220472 is an abundant number, since it is smaller than the sum of its proper divisors (28400008).

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

21220472 is a wasteful number, since it uses less digits than its factorization.

21220472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412 (or 408 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 21220472 is about 4606.5683539919. The cubic root of 21220472 is about 276.8545592276.

Adding to 21220472 its reverse (27402212), we get a palindrome (48622684).

The spelling of 21220472 in words is "twenty-one million, two hundred twenty thousand, four hundred seventy-two".