878217921 has 24 divisors (see below), whose sum is σ = 1464712704. Its totient is φ = 496661760.

The previous prime is 878217917. The next prime is 878217979. The reversal of 878217921 is 129712878.

It is not a de Polignac number, because 878217921 - 2² = 878217917 is a prime.

It is not an unprimeable number, because it can be changed into a prime (878217721) 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, 65745 + ... + 77966.

It is an arithmetic number, because the mean of its divisors is an integer number (61029696).

Almost surely, 2^878217921 is an apocalyptic number.

It is an amenable number.

878217921 is a deficient number, since it is larger than the sum of its proper divisors (586494783).

878217921 is a wasteful number, since it uses less digits than its factorization.

878217921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143821 (or 143818 counting only the distinct ones).

The product of its digits is 112896, while the sum is 45.

The square root of 878217921 is about 29634.7417906753. The cubic root of 878217921 is about 957.6366639072.

The spelling of 878217921 in words is "eight hundred seventy-eight million, two hundred seventeen thousand, nine hundred twenty-one".