1216538181 has 24 divisors (see below), whose sum is σ = 1775469696. Its totient is φ = 802638720.

The previous prime is 1216538131. The next prime is 1216538227. The reversal of 1216538181 is 1818356121.

It is not a de Polignac number, because 1216538181 - 2¹³ = 1216529989 is a prime.

It is a super-2 number, since 2×1216538181² = 2959930291661577522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216538131) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 509316 + ... + 511698.

It is an arithmetic number, because the mean of its divisors is an integer number (73977904).

Almost surely, 2^1216538181 is an apocalyptic number.

It is an amenable number.

1216538181 is a deficient number, since it is larger than the sum of its proper divisors (558931515).

1216538181 is a wasteful number, since it uses less digits than its factorization.

1216538181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2953 (or 2950 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 1216538181 is about 34878.9073940111. The cubic root of 1216538181 is about 1067.5181015127.

The spelling of 1216538181 in words is "one billion, two hundred sixteen million, five hundred thirty-eight thousand, one hundred eighty-one".