1216556121 has 16 divisors (see below), whose sum is σ = 1770137280. Its totient is φ = 737056320.

The previous prime is 1216556093. The next prime is 1216556179.

1216556121 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1216556121 - 2¹⁵ = 1216523353 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1216556021) 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, 152295 + ... + 160083.

It is an arithmetic number, because the mean of its divisors is an integer number (110633580).

Almost surely, 2^1216556121 is an apocalyptic number.

1216556121 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1216556121 is a deficient number, since it is larger than the sum of its proper divisors (553581159).

1216556121 is a wasteful number, since it uses less digits than its factorization.

1216556121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12536.

The product of its digits is 3600, while the sum is 30.

The square root of 1216556121 is about 34879.1645685501. The cubic root of 1216556121 is about 1067.5233489656.

It can be divided in two parts, 12165 and 56121, that added together give a palindrome (68286).

The spelling of 1216556121 in words is "one billion, two hundred sixteen million, five hundred fifty-six thousand, one hundred twenty-one".