28987781 has 2 divisors, whose sum is σ = 28987782. Its totient is φ = 28987780.

The previous prime is 28987769. The next prime is 28987793. The reversal of 28987781 is 18778982.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (28987769) and next prime (28987793).

It can be written as a sum of positive squares in only one way, i.e., 24108100 + 4879681 = 4910^2 + 2209^2 .

It is a cyclic number.

It is not a de Polignac number, because 28987781 - 2²² = 24793477 is a prime.

It is a super-2 number, since 2×28987781² = 1680582894607922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28987681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14493890 + 14493891.

It is an arithmetic number, because the mean of its divisors is an integer number (14493891).

Almost surely, 2^28987781 is an apocalyptic number.

It is an amenable number.

28987781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28987781 is an equidigital number, since it uses as much as digits as its factorization.

28987781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 451584, while the sum is 50.

The square root of 28987781 is about 5384.0301819362. The cubic root of 28987781 is about 307.1885263467.

The spelling of 28987781 in words is "twenty-eight million, nine hundred eighty-seven thousand, seven hundred eighty-one".