28138925917 has 4 divisors (see below), whose sum is σ = 28170866556. Its totient is φ = 28106985280.

The previous prime is 28138925869. The next prime is 28138925921. The reversal of 28138925917 is 71952983182.

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 5416076836 + 22722849081 = 73594^2 + 150741^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28138925917 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28138925977) 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, 15968998 + ... + 15970759.

It is an arithmetic number, because the mean of its divisors is an integer number (7042716639).

Almost surely, 2^28138925917 is an apocalyptic number.

It is an amenable number.

28138925917 is a deficient number, since it is larger than the sum of its proper divisors (31940639).

28138925917 is an equidigital number, since it uses as much as digits as its factorization.

28138925917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31940638.

The product of its digits is 2177280, while the sum is 55.

The spelling of 28138925917 in words is "twenty-eight billion, one hundred thirty-eight million, nine hundred twenty-five thousand, nine hundred seventeen".