221205620 has 24 divisors (see below), whose sum is σ = 480551400. Its totient is φ = 85430912.

The previous prime is 221205617. The next prime is 221205629. The reversal of 221205620 is 26502122.

It can be written as a sum of positive squares in 4 ways, for example, as 7695076 + 213510544 = 2774^2 + 14612^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 221205592 and 221205601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221205629) 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, 190115 + ... + 191274.

It is an arithmetic number, because the mean of its divisors is an integer number (20022975).

Almost surely, 2^221205620 is an apocalyptic number.

221205620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221205620 is an abundant number, since it is smaller than the sum of its proper divisors (259345780).

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

221205620 is a wasteful number, since it uses less digits than its factorization.

221205620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 381427 (or 381425 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 221205620 is about 14872.9828884457. The cubic root of 221205620 is about 604.7818078020.

Adding to 221205620 its reverse (26502122), we get a palindrome (247707742).

The spelling of 221205620 in words is "two hundred twenty-one million, two hundred five thousand, six hundred twenty".