72128779 has 4 divisors (see below), whose sum is σ = 73311280. Its totient is φ = 70946280.

The previous prime is 72128753. The next prime is 72128801. The reversal of 72128779 is 97782127.

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: 97782127 = 1297 ⋅75391.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72128779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72128279) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 591159 + ... + 591280.

It is an arithmetic number, because the mean of its divisors is an integer number (18327820).

Almost surely, 2^72128779 is an apocalyptic number.

72128779 is a deficient number, since it is larger than the sum of its proper divisors (1182501).

72128779 is a wasteful number, since it uses less digits than its factorization.

72128779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1182500.

The product of its digits is 98784, while the sum is 43.

The square root of 72128779 is about 8492.8663594808. The cubic root of 72128779 is about 416.2646456925.

The spelling of 72128779 in words is "seventy-two million, one hundred twenty-eight thousand, seven hundred seventy-nine".