78331891 has 6 divisors (see below), whose sum is σ = 86100476. Its totient is φ = 71210700.

The previous prime is 78331867. The next prime is 78331907. The reversal of 78331891 is 19813387.

It is not a de Polignac number, because 78331891 - 2¹³ = 78323699 is a prime.

It is a super-2 number, since 2×78331891² = 12271770295271762, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78331861) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 323565 + ... + 323806.

Almost surely, 2^78331891 is an apocalyptic number.

78331891 is a deficient number, since it is larger than the sum of its proper divisors (7768585).

78331891 is a wasteful number, since it uses less digits than its factorization.

78331891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 647393 (or 647382 counting only the distinct ones).

The product of its digits is 36288, while the sum is 40.

The square root of 78331891 is about 8850.5305490688. The cubic root of 78331891 is about 427.8710179219.

The spelling of 78331891 in words is "seventy-eight million, three hundred thirty-one thousand, eight hundred ninety-one".