28218731 has 2 divisors, whose sum is σ = 28218732. Its totient is φ = 28218730.

The previous prime is 28218727. The next prime is 28218733. The reversal of 28218731 is 13781282.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 28218731 - 2² = 28218727 is a prime.

It is a super-2 number, since 2×28218731² = 1592593558500722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 28218733, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_1754168 and since 28218731 and 1754168 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (28218733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14109365 + 14109366.

It is an arithmetic number, because the mean of its divisors is an integer number (14109366).

Almost surely, 2^28218731 is an apocalyptic number.

28218731 is a deficient number, since it is larger than the sum of its proper divisors (1).

28218731 is an equidigital number, since it uses as much as digits as its factorization.

28218731 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5376, while the sum is 32.

The square root of 28218731 is about 5312.1305518596. The cubic root of 28218731 is about 304.4475568093.

The spelling of 28218731 in words is "twenty-eight million, two hundred eighteen thousand, seven hundred thirty-one".