28997921 has 2 divisors, whose sum is σ = 28997922. Its totient is φ = 28997920.

The previous prime is 28997911. The next prime is 28997923. The reversal of 28997921 is 12979982.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27709696 + 1288225 = 5264^2 + 1135^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28997921 is a prime.

Together with 28997923, it forms a pair of twin primes.

It is a Chen prime.

It is a pancake number, because a pancake can be divided into 28997921 parts by 7615 straight cuts.

It is not a weakly prime, because it can be changed into another prime (28997923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14498960 + 14498961.

It is an arithmetic number, because the mean of its divisors is an integer number (14498961).

Almost surely, 2^28997921 is an apocalyptic number.

It is an amenable number.

28997921 is a deficient number, since it is larger than the sum of its proper divisors (1).

28997921 is an equidigital number, since it uses as much as digits as its factorization.

28997921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 47.

The square root of 28997921 is about 5384.9717733708. The cubic root of 28997921 is about 307.2243406153.

The spelling of 28997921 in words is "twenty-eight million, nine hundred ninety-seven thousand, nine hundred twenty-one".