1211220816 has 80 divisors (see below), whose sum is σ = 3547064640. Its totient is φ = 353064960.

The previous prime is 1211220793. The next prime is 1211220817. The reversal of 1211220816 is 6180221121.

It is a super-2 number, since 2×1211220816² = 2934111730223411712, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211220817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39225 + ... + 62936.

It is an arithmetic number, because the mean of its divisors is an integer number (44338308).

Almost surely, 2^1211220816 is an apocalyptic number.

1211220816 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1211220816 is an abundant number, since it is smaller than the sum of its proper divisors (2335843824).

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

1211220816 is a wasteful number, since it uses less digits than its factorization.

1211220816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102204 (or 102198 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 1211220816 is about 34802.5978340698. The cubic root of 1211220816 is about 1065.9604921370.

Adding to 1211220816 its reverse (6180221121), we get a palindrome (7391441937).

The spelling of 1211220816 in words is "one billion, two hundred eleven million, two hundred twenty thousand, eight hundred sixteen".