78121836 has 72 divisors (see below), whose sum is σ = 215458880. Its totient is φ = 23721984.

The previous prime is 78121819. The next prime is 78121843. The reversal of 78121836 is 63812187.

It is a super-2 number, since 2×78121836² = 12206042520021792, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an alternating number because its digits alternate between odd and even.

It is a self number, because there is not a number n which added to its sum of digits gives 78121836.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35916 + ... + 38028.

Almost surely, 2^78121836 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 78121836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107729440).

78121836 is an abundant number, since it is smaller than the sum of its proper divisors (137337044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

78121836 is a wasteful number, since it uses less digits than its factorization.

78121836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2215 (or 2210 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 78121836 is about 8838.6557801512. The cubic root of 78121836 is about 427.4882155364.

The spelling of 78121836 in words is "seventy-eight million, one hundred twenty-one thousand, eight hundred thirty-six".