20217617840978 has 16 divisors (see below), whose sum is σ = 30451438028160. Its totient is φ = 10067205548400.

The previous prime is 20217617840977. The next prime is 20217617841061. The reversal of 20217617840978 is 87904871671202.

It is a self number, because there is not a number n which added to its sum of digits gives 20217617840978.

It is not an unprimeable number, because it can be changed into a prime (20217617840971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16158833 + ... + 17364996.

It is an arithmetic number, because the mean of its divisors is an integer number (1903214876760).

Almost surely, 2^{20217617840978} is an apocalyptic number.

20217617840978 is a deficient number, since it is larger than the sum of its proper divisors (10233820187182).

20217617840978 is a wasteful number, since it uses less digits than its factorization.

20217617840978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33525073.

The product of its (nonzero) digits is 18966528, while the sum is 62.

The spelling of 20217617840978 in words is "twenty trillion, two hundred seventeen billion, six hundred seventeen million, eight hundred forty thousand, nine hundred seventy-eight".