28128531577 has 4 divisors (see below), whose sum is σ = 28129026816. Its totient is φ = 28128036340.

The previous prime is 28128531533. The next prime is 28128531581. The reversal of 28128531577 is 77513582182.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28128531577 is a prime.

It is a super-2 number, since 2×28128531577² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28128531577.

It is not an unprimeable number, because it can be changed into a prime (28128531077) 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, 149449 + ... + 280342.

It is an arithmetic number, because the mean of its divisors is an integer number (7032256704).

Almost surely, 2^28128531577 is an apocalyptic number.

It is an amenable number.

28128531577 is a deficient number, since it is larger than the sum of its proper divisors (495239).

28128531577 is an equidigital number, since it uses as much as digits as its factorization.

28128531577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495238.

The product of its digits is 940800, while the sum is 49.

The spelling of 28128531577 in words is "twenty-eight billion, one hundred twenty-eight million, five hundred thirty-one thousand, five hundred seventy-seven".