1215211720 has 32 divisors (see below), whose sum is σ = 2808127800. Its totient is φ = 472946688.

The previous prime is 1215211703. The next prime is 1215211807. The reversal of 1215211720 is 271125121.

It can be written as a sum of positive squares in 4 ways, for example, as 888397636 + 326814084 = 29806^2 + 18078^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1215211691 and 1215211700.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 409065 + ... + 412024.

Almost surely, 2^1215211720 is an apocalyptic number.

1215211720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1215211720 is an abundant number, since it is smaller than the sum of its proper divisors (1592916080).

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

1215211720 is a wasteful number, since it uses less digits than its factorization.

1215211720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 821137 (or 821133 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 22.

The square root of 1215211720 is about 34859.8869762941. The cubic root of 1215211720 is about 1067.1299684427.

Adding to 1215211720 its reverse (271125121), we get a palindrome (1486336841).

The spelling of 1215211720 in words is "one billion, two hundred fifteen million, two hundred eleven thousand, seven hundred twenty".