28157666021 has 2 divisors, whose sum is σ = 28157666022. Its totient is φ = 28157666020.

The previous prime is 28157666003. The next prime is 28157666023. The reversal of 28157666021 is 12066675182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28143753121 + 13912900 = 167761^2 + 3730^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28157666021 is a prime.

Together with 28157666023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28157666023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14078833010 + 14078833011.

It is an arithmetic number, because the mean of its divisors is an integer number (14078833011).

Almost surely, 2^28157666021 is an apocalyptic number.

It is an amenable number.

28157666021 is a deficient number, since it is larger than the sum of its proper divisors (1).

28157666021 is an equidigital number, since it uses as much as digits as its factorization.

28157666021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 241920, while the sum is 44.

The spelling of 28157666021 in words is "twenty-eight billion, one hundred fifty-seven million, six hundred sixty-six thousand, twenty-one".