1215209778 has 16 divisors (see below), whose sum is σ = 2436225120. Its totient is φ = 404102336.

The previous prime is 1215209777. The next prime is 1215209789. The reversal of 1215209778 is 8779025121.

It is not an unprimeable number, because it can be changed into a prime (1215209777) by changing a digit.

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, 239175 + ... + 244202.

It is an arithmetic number, because the mean of its divisors is an integer number (152264070).

Almost surely, 2^1215209778 is an apocalyptic number.

1215209778 is an abundant number, since it is smaller than the sum of its proper divisors (1221015342).

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

1215209778 is a wasteful number, since it uses less digits than its factorization.

1215209778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 483801.

The product of its (nonzero) digits is 70560, while the sum is 42.

The square root of 1215209778 is about 34859.8591219184. The cubic root of 1215209778 is about 1067.1293999910.

The spelling of 1215209778 in words is "one billion, two hundred fifteen million, two hundred nine thousand, seven hundred seventy-eight".