78215869 has 4 divisors (see below), whose sum is σ = 78247260. Its totient is φ = 78184480.

The previous prime is 78215843. The next prime is 78215873. The reversal of 78215869 is 96851287.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 96851287 = 13 ⋅7450099.

It can be written as a sum of positive squares in 2 ways, for example, as 76352644 + 1863225 = 8738^2 + 1365^2 .

It is a cyclic number.

It is not a de Polignac number, because 78215869 - 2²¹ = 76118717 is a prime.

It is a super-2 number, since 2×78215869² = 12235444326850322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78215369) 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, 11602 + ... + 17059.

It is an arithmetic number, because the mean of its divisors is an integer number (19561815).

Almost surely, 2^78215869 is an apocalyptic number.

It is an amenable number.

78215869 is a deficient number, since it is larger than the sum of its proper divisors (31391).

78215869 is a wasteful number, since it uses less digits than its factorization.

78215869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31390.

The product of its digits is 241920, while the sum is 46.

The square root of 78215869 is about 8843.9735978801. The cubic root of 78215869 is about 427.6596651755.

The spelling of 78215869 in words is "seventy-eight million, two hundred fifteen thousand, eight hundred sixty-nine".