28908235981 has 4 divisors (see below), whose sum is σ = 28910110464. Its totient is φ = 28906361500.

The previous prime is 28908235949. The next prime is 28908235987. The reversal of 28908235981 is 18953280982.

It is a happy number.

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 not a de Polignac number, because 28908235981 - 2⁵ = 28908235949 is a prime.

It is a super-2 number, since 2×28908235981² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28908235987) 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, 913915 + ... + 945016.

It is an arithmetic number, because the mean of its divisors is an integer number (7227527616).

Almost surely, 2^28908235981 is an apocalyptic number.

It is an amenable number.

28908235981 is a deficient number, since it is larger than the sum of its proper divisors (1874483).

28908235981 is a wasteful number, since it uses less digits than its factorization.

28908235981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1874482.

The product of its (nonzero) digits is 2488320, while the sum is 55.

It can be divided in two parts, 2890823 and 5981, that added together give a square (2896804 = 1702²).

The spelling of 28908235981 in words is "twenty-eight billion, nine hundred eight million, two hundred thirty-five thousand, nine hundred eighty-one".