1216809881 has 8 divisors (see below), whose sum is σ = 1416878784. Its totient is φ = 1023300720.

The previous prime is 1216809863. The next prime is 1216809899. The reversal of 1216809881 is 1889086121.

It is an interprime number because it is at equal distance from previous prime (1216809863) and next prime (1216809899).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1216809881 - 2²² = 1212615577 is a prime.

It is a super-2 number, since 2×1216809881² = 2961252572998468322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1216809851) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 1639535 + ... + 1640276.

It is an arithmetic number, because the mean of its divisors is an integer number (177109848).

Almost surely, 2^1216809881 is an apocalyptic number.

It is an amenable number.

1216809881 is a deficient number, since it is larger than the sum of its proper divisors (200068903).

1216809881 is an equidigital number, since it uses as much as digits as its factorization.

1216809881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3279871.

The product of its (nonzero) digits is 55296, while the sum is 44.

The square root of 1216809881 is about 34882.8020806815. The cubic root of 1216809881 is about 1067.5975682823.

The spelling of 1216809881 in words is "one billion, two hundred sixteen million, eight hundred nine thousand, eight hundred eighty-one".