28656879721 has 2 divisors, whose sum is σ = 28656879722. Its totient is φ = 28656879720.

The previous prime is 28656879703. The next prime is 28656879733. The reversal of 28656879721 is 12797865682.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 24051357225 + 4605522496 = 155085^2 + 67864^2 .

It is a cyclic number.

It is not a de Polignac number, because 28656879721 - 2⁷ = 28656879593 is a prime.

It is a super-2 number, since 2×28656879721² (a number of 22 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 28656879721.

It is not a weakly prime, because it can be changed into another prime (28656849721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14328439860 + 14328439861.

It is an arithmetic number, because the mean of its divisors is an integer number (14328439861).

Almost surely, 2^28656879721 is an apocalyptic number.

It is an amenable number.

28656879721 is a deficient number, since it is larger than the sum of its proper divisors (1).

28656879721 is an equidigital number, since it uses as much as digits as its factorization.

28656879721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20321280, while the sum is 61.

The spelling of 28656879721 in words is "twenty-eight billion, six hundred fifty-six million, eight hundred seventy-nine thousand, seven hundred twenty-one".