28091971 has 2 divisors, whose sum is σ = 28091972. Its totient is φ = 28091970.

The previous prime is 28091969. The next prime is 28091977. The reversal of 28091971 is 17919082.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 28091971 - 2¹ = 28091969 is a prime.

Together with 28091969, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 28091971.

It is not a weakly prime, because it can be changed into another prime (28091977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14045985 + 14045986.

It is an arithmetic number, because the mean of its divisors is an integer number (14045986).

Almost surely, 2^28091971 is an apocalyptic number.

28091971 is a deficient number, since it is larger than the sum of its proper divisors (1).

28091971 is an equidigital number, since it uses as much as digits as its factorization.

28091971 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 28091971 is about 5300.1859401346. The cubic root of 28091971 is about 303.9910077846.

The spelling of 28091971 in words is "twenty-eight million, ninety-one thousand, nine hundred seventy-one".