1216561394 has 4 divisors (see below), whose sum is σ = 1824842094. Its totient is φ = 608280696.

The previous prime is 1216561363. The next prime is 1216561399. The reversal of 1216561394 is 4931656121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 4931656121 = 7 ⋅704522303.

It can be written as a sum of positive squares in only one way, i.e., 1121245225 + 95316169 = 33485^2 + 9763^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1216561399) 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 as a sum of consecutive naturals, namely, 304140347 + ... + 304140350.

Almost surely, 2^1216561394 is an apocalyptic number.

1216561394 is a deficient number, since it is larger than the sum of its proper divisors (608280700).

1216561394 is an equidigital number, since it uses as much as digits as its factorization.

1216561394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608280699.

The product of its digits is 38880, while the sum is 38.

The square root of 1216561394 is about 34879.2401580080. The cubic root of 1216561394 is about 1067.5248913092.

The spelling of 1216561394 in words is "one billion, two hundred sixteen million, five hundred sixty-one thousand, three hundred ninety-four".