21220380 has 60 divisors (see below), whose sum is σ = 66574200. Its totient is φ = 5658336.

The previous prime is 21220379. The next prime is 21220391. The reversal of 21220380 is 8302212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (60).

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4930 + ... + 8169.

It is an arithmetic number, because the mean of its divisors is an integer number (1109570).

Almost surely, 2^21220380 is an apocalyptic number.

21220380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21220380 is an abundant number, since it is smaller than the sum of its proper divisors (45353820).

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

21220380 is a wasteful number, since it uses less digits than its factorization.

21220380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13120 (or 13109 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21220380 is about 4606.5583682398. The cubic root of 21220380 is about 276.8541591319.

Adding to 21220380 its reverse (8302212), we get a palindrome (29522592).

The spelling of 21220380 in words is "twenty-one million, two hundred twenty thousand, three hundred eighty".