28056137221 has 24 divisors (see below), whose sum is σ = 34633963800. Its totient is φ = 22582812672.

The previous prime is 28056137209. The next prime is 28056137281. The reversal of 28056137221 is 12273165082.

It can be written as a sum of positive squares in 4 ways, for example, as 17453316321 + 10602820900 = 132111^2 + 102970^2 .

It is a de Polignac number, because none of the positive numbers 2^k-28056137221 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 (28056137281) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 336511 + ... + 411523.

It is an arithmetic number, because the mean of its divisors is an integer number (1443081825).

Almost surely, 2^28056137221 is an apocalyptic number.

It is an amenable number.

28056137221 is a deficient number, since it is larger than the sum of its proper divisors (6577826579).

28056137221 is a wasteful number, since it uses less digits than its factorization.

28056137221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75493 (or 75486 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 37.

The spelling of 28056137221 in words is "twenty-eight billion, fifty-six million, one hundred thirty-seven thousand, two hundred twenty-one".