78145891 has 4 divisors (see below), whose sum is σ = 78283800. Its totient is φ = 78007984.

The previous prime is 78145883. The next prime is 78145967. The reversal of 78145891 is 19854187.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19854187 = 751 ⋅26437.

It is a cyclic number.

It is not a de Polignac number, because 78145891 - 2³ = 78145883 is a prime.

It is a super-2 number, since 2×78145891² = 12213560560367762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78145801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68101 + ... + 69238.

It is an arithmetic number, because the mean of its divisors is an integer number (19570950).

Almost surely, 2^78145891 is an apocalyptic number.

78145891 is a deficient number, since it is larger than the sum of its proper divisors (137909).

78145891 is a wasteful number, since it uses less digits than its factorization.

78145891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137908.

The product of its digits is 80640, while the sum is 43.

The square root of 78145891 is about 8840.0164592607. The cubic root of 78145891 is about 427.5320879212.

The spelling of 78145891 in words is "seventy-eight million, one hundred forty-five thousand, eight hundred ninety-one".