78121839 has 4 divisors (see below), whose sum is σ = 104162456. Its totient is φ = 52081224.

The previous prime is 78121819. The next prime is 78121843. The reversal of 78121839 is 93812187.

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

It is not a de Polignac number, because 78121839 - 2⁹ = 78121327 is a prime.

It is a super-2 number, since 2×78121839² = 12206043457483842, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 78121797 and 78121806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78121819) 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, 13020304 + ... + 13020309.

It is an arithmetic number, because the mean of its divisors is an integer number (26040614).

Almost surely, 2^78121839 is an apocalyptic number.

78121839 is a deficient number, since it is larger than the sum of its proper divisors (26040617).

78121839 is a wasteful number, since it uses less digits than its factorization.

78121839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26040616.

The product of its digits is 24192, while the sum is 39.

The square root of 78121839 is about 8838.6559498603. The cubic root of 78121839 is about 427.4882210085.

The spelling of 78121839 in words is "seventy-eight million, one hundred twenty-one thousand, eight hundred thirty-nine".