78120209 has 4 divisors (see below), whose sum is σ = 80231604. Its totient is φ = 76008816.

The previous prime is 78120197. The next prime is 78120233. The reversal of 78120209 is 90202187.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 50452609 + 27667600 = 7103^2 + 5260^2 .

It is a cyclic number.

It is not a de Polignac number, because 78120209 - 2⁴ = 78120193 is a prime.

It is a super-2 number, since 2×78120209² = 12205534108407362, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (78120239) 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, 1055642 + ... + 1055715.

It is an arithmetic number, because the mean of its divisors is an integer number (20057901).

Almost surely, 2^78120209 is an apocalyptic number.

It is an amenable number.

78120209 is a deficient number, since it is larger than the sum of its proper divisors (2111395).

78120209 is a wasteful number, since it uses less digits than its factorization.

78120209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2111394.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 78120209 is about 8838.5637407896. The cubic root of 78120209 is about 427.4852478295.

The spelling of 78120209 in words is "seventy-eight million, one hundred twenty thousand, two hundred nine".