1221016720 has 160 divisors (see below), whose sum is σ = 3555486720. Its totient is φ = 378846720.

The previous prime is 1221016711. The next prime is 1221016729. The reversal of 1221016720 is 276101221.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1221016711) and next prime (1221016729).

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a junction number, because it is equal to n+sod(n) for n = 1221016691 and 1221016700.

It is not an unprimeable number, because it can be changed into a prime (1221016729) 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 31 ways as a sum of consecutive naturals, for example, 2334379 + ... + 2334901.

It is an arithmetic number, because the mean of its divisors is an integer number (22221792).

Almost surely, 2^1221016720 is an apocalyptic number.

1221016720 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 1221016720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1777743360).

1221016720 is an abundant number, since it is smaller than the sum of its proper divisors (2334470000).

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

1221016720 is a wasteful number, since it uses less digits than its factorization.

1221016720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 933 (or 927 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 22.

The square root of 1221016720 is about 34943.0496665646. The cubic root of 1221016720 is about 1068.8264771146.

Adding to 1221016720 its reverse (276101221), we get a palindrome (1497117941).

It can be divided in two parts, 122101 and 6720, that added together give a palindrome (128821).

The spelling of 1221016720 in words is "one billion, two hundred twenty-one million, sixteen thousand, seven hundred twenty".