221220100 has 36 divisors (see below), whose sum is σ = 484320564. Its totient is φ = 87700480.

The previous prime is 221220089. The next prime is 221220101. The reversal of 221220100 is 1022122.

It can be written as a sum of positive squares in 6 ways, for example, as 7884864 + 213335236 = 2808^2 + 14606^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is not an unprimeable number, because it can be changed into a prime (221220101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1512 + ... + 21088.

It is an arithmetic number, because the mean of its divisors is an integer number (13453349).

Almost surely, 2^221220100 is an apocalyptic number.

221220100 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 221220100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (242160282).

221220100 is an abundant number, since it is smaller than the sum of its proper divisors (263100464).

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

221220100 is a wasteful number, since it uses less digits than its factorization.

221220100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19704 (or 19697 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 221220100 is about 14873.4696691794. The cubic root of 221220100 is about 604.7950037438.

Adding to 221220100 its reverse (1022122), we get a palindrome (222242222).

The spelling of 221220100 in words is "two hundred twenty-one million, two hundred twenty thousand, one hundred".