1221003220 has 12 divisors (see below), whose sum is σ = 2564106804. Its totient is φ = 488401280.

The previous prime is 1221003209. The next prime is 1221003227. The reversal of 1221003220 is 223001221.

It can be written as a sum of positive squares in 2 ways, for example, as 364504464 + 856498756 = 19092^2 + 29266^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1221003220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221003227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30525061 + ... + 30525100.

It is an arithmetic number, because the mean of its divisors is an integer number (213675567).

Almost surely, 2^1221003220 is an apocalyptic number.

1221003220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221003220 is an abundant number, since it is smaller than the sum of its proper divisors (1343103584).

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

1221003220 is a wasteful number, since it uses less digits than its factorization.

1221003220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61050170 (or 61050168 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 1221003220 is about 34942.8564945684. The cubic root of 1221003220 is about 1068.8225379901.

Adding to 1221003220 its reverse (223001221), we get a palindrome (1444004441).

The spelling of 1221003220 in words is "one billion, two hundred twenty-one million, three thousand, two hundred twenty".