21220100 has 72 divisors (see below), whose sum is σ = 50996736. Its totient is φ = 7600000.

The previous prime is 21220019. The next prime is 21220103. The reversal of 21220100 is 102212.

It is not an unprimeable number, because it can be changed into a prime (21220103) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 111005 + ... + 111195.

It is an arithmetic number, because the mean of its divisors is an integer number (708288).

Almost surely, 2^21220100 is an apocalyptic number.

21220100 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 21220100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25498368).

21220100 is an abundant number, since it is smaller than the sum of its proper divisors (29776636).

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

21220100 is a wasteful number, since it uses less digits than its factorization.

21220100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317 (or 310 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 21220100 is about 4606.5279766870. The cubic root of 21220100 is about 276.8529414424.

Adding to 21220100 its reverse (102212), we get a palindrome (21322312).

The spelling of 21220100 in words is "twenty-one million, two hundred twenty thousand, one hundred".