1216520720 has 20 divisors (see below), whose sum is σ = 2828410860. Its totient is φ = 486608256.

The previous prime is 1216520707. The next prime is 1216520741. The reversal of 1216520720 is 270256121.

It can be written as a sum of positive squares in 2 ways, for example, as 262699264 + 953821456 = 16208^2 + 30884^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a self number, because there is not a number n which added to its sum of digits gives 1216520720.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7603175 + ... + 7603334.

It is an arithmetic number, because the mean of its divisors is an integer number (141420543).

Almost surely, 2^1216520720 is an apocalyptic number.

1216520720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1216520720 is an abundant number, since it is smaller than the sum of its proper divisors (1611890140).

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

1216520720 is a wasteful number, since it uses less digits than its factorization.

1216520720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15206522 (or 15206516 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 1216520720 is about 34878.6570842399. The cubic root of 1216520720 is about 1067.5129941177.

Adding to 1216520720 its reverse (270256121), we get a palindrome (1486776841).

The spelling of 1216520720 in words is "one billion, two hundred sixteen million, five hundred twenty thousand, seven hundred twenty".