1211305305 has 32 divisors (see below), whose sum is σ = 2222095104. Its totient is φ = 551955456.

The previous prime is 1211305289. The next prime is 1211305331. The reversal of 1211305305 is 5035031121.

It is not a de Polignac number, because 1211305305 - 2⁴ = 1211305289 is a prime.

It is a super-2 number, since 2×1211305305² = 2934521083842286050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 14437 + ... + 51293.

It is an arithmetic number, because the mean of its divisors is an integer number (69440472).

Almost surely, 2^1211305305 is an apocalyptic number.

1211305305 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1211305305 is a deficient number, since it is larger than the sum of its proper divisors (1010789799).

1211305305 is a wasteful number, since it uses less digits than its factorization.

1211305305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37185.

The product of its (nonzero) digits is 450, while the sum is 21.

The square root of 1211305305 is about 34803.8116447035. The cubic root of 1211305305 is about 1065.9852770044.

Adding to 1211305305 its reverse (5035031121), we get a palindrome (6246336426).

The spelling of 1211305305 in words is "one billion, two hundred eleven million, three hundred five thousand, three hundred five".