7878385921 has 16 divisors (see below), whose sum is σ = 9138873600. Its totient is φ = 6652324800.

The previous prime is 7878385901. The next prime is 7878385961. The reversal of 7878385921 is 1295838787.

It is a cyclic number.

It is not a de Polignac number, because 7878385921 - 2¹⁹ = 7877861633 is a prime.

It is a super-2 number, since 2×7878385921² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7878385901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 112695 + ... + 168691.

It is an arithmetic number, because the mean of its divisors is an integer number (571179600).

Almost surely, 2^7878385921 is an apocalyptic number.

It is an amenable number.

7878385921 is a deficient number, since it is larger than the sum of its proper divisors (1260487679).

7878385921 is a wasteful number, since it uses less digits than its factorization.

7878385921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56304.

The product of its digits is 6773760, while the sum is 58.

The square root of 7878385921 is about 88760.2721998981. The cubic root of 7878385921 is about 1989.8137011527.

The spelling of 7878385921 in words is "seven billion, eight hundred seventy-eight million, three hundred eighty-five thousand, nine hundred twenty-one".