1221004720 has 80 divisors (see below), whose sum is σ = 3075740640. Its totient is φ = 450767616.

The previous prime is 1221004709. The next prime is 1221004727. The reversal of 1221004720 is 274001221.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (1221004727) 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 15 ways as a sum of consecutive naturals, for example, 172287 + ... + 179233.

It is an arithmetic number, because the mean of its divisors is an integer number (38446758).

Almost surely, 2^1221004720 is an apocalyptic number.

1221004720 is a gapful number since it is divisible by the number (10) 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 1221004720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1537870320).

1221004720 is an abundant number, since it is smaller than the sum of its proper divisors (1854735920).

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

1221004720 is an equidigital number, since it uses as much as digits as its factorization.

1221004720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6999 (or 6967 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 1221004720 is about 34942.8779581763. The cubic root of 1221004720 is about 1068.8229756720.

Adding to 1221004720 its reverse (274001221), we get a palindrome (1495005941).

The spelling of 1221004720 in words is "one billion, two hundred twenty-one million, four thousand, seven hundred twenty".