81858779 has 4 divisors (see below), whose sum is σ = 81881184. Its totient is φ = 81836376.

The previous prime is 81858743. The next prime is 81858781. The reversal of 81858779 is 97785818.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81858779 - 2²⁴ = 65081563 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81858779.

It is not an unprimeable number, because it can be changed into a prime (81858719) 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, 4307 + ... + 13500.

It is an arithmetic number, because the mean of its divisors is an integer number (20470296).

Almost surely, 2^81858779 is an apocalyptic number.

81858779 is a deficient number, since it is larger than the sum of its proper divisors (22405).

81858779 is a wasteful number, since it uses less digits than its factorization.

81858779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22404.

The product of its digits is 1128960, while the sum is 53.

The square root of 81858779 is about 9047.5841526896. The cubic root of 81858779 is about 434.1986020049.

The spelling of 81858779 in words is "eighty-one million, eight hundred fifty-eight thousand, seven hundred seventy-nine".