1221543778 has 32 divisors (see below), whose sum is σ = 2327915520. Its totient is φ = 467657280.

The previous prime is 1221543773. The next prime is 1221543787. The reversal of 1221543778 is 8773451221.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221543778.

It is not an unprimeable number, because it can be changed into a prime (1221543773) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 102613 + ... + 113896.

It is an arithmetic number, because the mean of its divisors is an integer number (72747360).

Almost surely, 2^1221543778 is an apocalyptic number.

1221543778 is a deficient number, since it is larger than the sum of its proper divisors (1106371742).

1221543778 is a wasteful number, since it uses less digits than its factorization.

1221543778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216562.

The product of its digits is 94080, while the sum is 40.

The square root of 1221543778 is about 34950.5905243388. The cubic root of 1221543778 is about 1068.9802430978.

Adding to 1221543778 its reverse (8773451221), we get a palindrome (9994994999).

The spelling of 1221543778 in words is "one billion, two hundred twenty-one million, five hundred forty-three thousand, seven hundred seventy-eight".