21447220 has 24 divisors (see below), whose sum is σ = 45549000. Its totient is φ = 8481792.

The previous prime is 21447203. The next prime is 21447229. The reversal of 21447220 is 2274412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1340964 + 20106256 = 1158^2 + 4484^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21447191 and 21447200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21447229) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4245 + ... + 7804.

It is an arithmetic number, because the mean of its divisors is an integer number (1897875).

Almost surely, 2^21447220 is an apocalyptic number.

21447220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21447220 is an abundant number, since it is smaller than the sum of its proper divisors (24101780).

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

21447220 is a wasteful number, since it uses less digits than its factorization.

21447220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12147 (or 12145 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21447220 is about 4631.1143367445. The cubic root of 21447220 is about 277.8371628886.

The spelling of 21447220 in words is "twenty-one million, four hundred forty-seven thousand, two hundred twenty".