2121218978 has 18 divisors (see below), whose sum is σ = 3298267089. Its totient is φ = 1023124872.

The previous prime is 2121218971. The next prime is 2121218987. The reversal of 2121218978 is 8798121212.

It can be written as a sum of positive squares in 2 ways, for example, as 2119957849 + 1261129 = 46043^2 + 1123^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=32567.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2121218971) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1888325 + ... + 1889447.

Almost surely, 2^2121218978 is an apocalyptic number.

2121218978 is a deficient number, since it is larger than the sum of its proper divisors (1177048111).

2121218978 is an frugal number, since it uses more digits than its factorization.

2121218978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2306 (or 1154 counting only the distinct ones).

The product of its digits is 32256, while the sum is 41.

The square root of 2121218978 is about 46056.6930858046. The cubic root of 2121218978 is about 1284.8778271609.

The spelling of 2121218978 in words is "two billion, one hundred twenty-one million, two hundred eighteen thousand, nine hundred seventy-eight".