1221055220 has 48 divisors (see below), whose sum is σ = 3196948608. Its totient is φ = 380588160.

The previous prime is 1221055207. The next prime is 1221055259. The reversal of 1221055220 is 225501221.

It is a happy number.

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 = 1221055192 and 1221055201.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 394907 + ... + 397986.

It is an arithmetic number, because the mean of its divisors is an integer number (66603096).

Almost surely, 2^1221055220 is an apocalyptic number.

1221055220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221055220 is an abundant number, since it is smaller than the sum of its proper divisors (1975893388).

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

1221055220 is a wasteful number, since it uses less digits than its factorization.

1221055220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 792920 (or 792918 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 1221055220 is about 34943.6005586144. The cubic root of 1221055220 is about 1068.8377107546.

Adding to 1221055220 its reverse (225501221), we get a palindrome (1446556441).

It can be divided in two parts, 1221055 and 220, that multiplied together give a square (268632100 = 16390²).

The spelling of 1221055220 in words is "one billion, two hundred twenty-one million, fifty-five thousand, two hundred twenty".