28042991 has 4 divisors (see below), whose sum is σ = 28332192. Its totient is φ = 27753792.

The previous prime is 28042969. The next prime is 28043011. The reversal of 28042991 is 19924082.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28042991 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 (28042951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144455 + ... + 144648.

It is an arithmetic number, because the mean of its divisors is an integer number (7083048).

Almost surely, 2^28042991 is an apocalyptic number.

28042991 is a deficient number, since it is larger than the sum of its proper divisors (289201).

28042991 is an equidigital number, since it uses as much as digits as its factorization.

28042991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289200.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 28042991 is about 5295.5633316957. The cubic root of 28042991 is about 303.8142296165.

The spelling of 28042991 in words is "twenty-eight million, forty-two thousand, nine hundred ninety-one".