78457821811 has 4 divisors (see below), whose sum is σ = 78458900632. Its totient is φ = 78456742992.

The previous prime is 78457821781. The next prime is 78457821821. The reversal of 78457821811 is 11812875487.

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: 11812875487 = 7 ⋅1687553641.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78457821811 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78457821821) 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, 421770 + ... + 578623.

It is an arithmetic number, because the mean of its divisors is an integer number (19614725158).

Almost surely, 2^78457821811 is an apocalyptic number.

78457821811 is a deficient number, since it is larger than the sum of its proper divisors (1078821).

78457821811 is a wasteful number, since it uses less digits than its factorization.

78457821811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1078820.

The product of its digits is 1003520, while the sum is 52.

The spelling of 78457821811 in words is "seventy-eight billion, four hundred fifty-seven million, eight hundred twenty-one thousand, eight hundred eleven".