1220721660 has 72 divisors (see below), whose sum is σ = 3707305056. Its totient is φ = 325134720.

The previous prime is 1220721641. The next prime is 1220721661. The reversal of 1220721660 is 661270221.

It is a super-2 number, since 2×1220721660² = 2980322742386311200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1220721661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 165777 + ... + 172983.

It is an arithmetic number, because the mean of its divisors is an integer number (51490348).

Almost surely, 2^1220721660 is an apocalyptic number.

1220721660 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1220721660 is an abundant number, since it is smaller than the sum of its proper divisors (2486583396).

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

1220721660 is a wasteful number, since it uses less digits than its factorization.

1220721660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8163 (or 8158 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 1220721660 is about 34938.8273987551. The cubic root of 1220721660 is about 1068.7403758239.

Adding to 1220721660 its reverse (661270221), we get a palindrome (1881991881).

The spelling of 1220721660 in words is "one billion, two hundred twenty million, seven hundred twenty-one thousand, six hundred sixty".