1216215945 has 128 divisors (see below), whose sum is σ = 2554675200. Its totient is φ = 537497856.

The previous prime is 1216215943. The next prime is 1216215947. The reversal of 1216215945 is 5495126121.

1216215945 is a `hidden beast` number, since 1 + 2 + 1 + 62 + 1 + 594 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (1216215943) and next prime (1216215947).

It is not a de Polignac number, because 1216215945 - 2¹ = 1216215943 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1216215943) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 6173587 + ... + 6173783.

It is an arithmetic number, because the mean of its divisors is an integer number (19958400).

Almost surely, 2^1216215945 is an apocalyptic number.

1216215945 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1216215945 is an abundant number, since it is smaller than the sum of its proper divisors (1338459255).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1216215945 is a wasteful number, since it uses less digits than its factorization.

1216215945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404 (or 398 counting only the distinct ones).

The product of its digits is 21600, while the sum is 36.

The square root of 1216215945 is about 34874.2877346621. The cubic root of 1216215945 is about 1067.4238386431.

The spelling of 1216215945 in words is "one billion, two hundred sixteen million, two hundred fifteen thousand, nine hundred forty-five".