78815861 has 4 divisors (see below), whose sum is σ = 80648832. Its totient is φ = 76982892.

The previous prime is 78815839. The next prime is 78815897. The reversal of 78815861 is 16851887.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78815861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78815801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 916421 + ... + 916506.

It is an arithmetic number, because the mean of its divisors is an integer number (20162208).

Almost surely, 2^78815861 is an apocalyptic number.

It is an amenable number.

78815861 is a deficient number, since it is larger than the sum of its proper divisors (1832971).

78815861 is a wasteful number, since it uses less digits than its factorization.

78815861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832970.

The product of its digits is 107520, while the sum is 44.

The square root of 78815861 is about 8877.8297460584. The cubic root of 78815861 is about 428.7504031480.

The spelling of 78815861 in words is "seventy-eight million, eight hundred fifteen thousand, eight hundred sixty-one".