1211516605 has 16 divisors (see below), whose sum is σ = 1633726080. Its totient is φ = 855759168.

The previous prime is 1211516539. The next prime is 1211516609. The reversal of 1211516605 is 5066151121.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1211516605 - 2¹⁷ = 1211385533 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211516609) 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, 403695 + ... + 406684.

It is an arithmetic number, because the mean of its divisors is an integer number (102107880).

Almost surely, 2^1211516605 is an apocalyptic number.

It is an amenable number.

1211516605 is a deficient number, since it is larger than the sum of its proper divisors (422209475).

1211516605 is a wasteful number, since it uses less digits than its factorization.

1211516605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 810420.

The product of its (nonzero) digits is 1800, while the sum is 28.

The square root of 1211516605 is about 34806.8470993855. The cubic root of 1211516605 is about 1066.0472568626.

Adding to 1211516605 its reverse (5066151121), we get a palindrome (6277667726).

It can be divided in two parts, 1211516 and 605, that added together give a palindrome (1212121).

The spelling of 1211516605 in words is "one billion, two hundred eleven million, five hundred sixteen thousand, six hundred five".