28081643581 has 4 divisors (see below), whose sum is σ = 28083586432. Its totient is φ = 28079700732.

The previous prime is 28081643567. The next prime is 28081643609. The reversal of 28081643581 is 18534618082.

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 28081643581 - 2⁵ = 28081643549 is a prime.

It is a super-2 number, since 2×28081643581² (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 (28081643501) 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, 949581 + ... + 978706.

It is an arithmetic number, because the mean of its divisors is an integer number (7020896608).

Almost surely, 2^28081643581 is an apocalyptic number.

It is an amenable number.

28081643581 is a deficient number, since it is larger than the sum of its proper divisors (1942851).

28081643581 is a wasteful number, since it uses less digits than its factorization.

28081643581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1942850.

The product of its (nonzero) digits is 368640, while the sum is 46.

The spelling of 28081643581 in words is "twenty-eight billion, eighty-one million, six hundred forty-three thousand, five hundred eighty-one".