28156781 has 2 divisors, whose sum is σ = 28156782. Its totient is φ = 28156780.

The previous prime is 28156769. The next prime is 28156823. The reversal of 28156781 is 18765182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24700900 + 3455881 = 4970^2 + 1859^2 .

It is a cyclic number.

It is not a de Polignac number, because 28156781 - 2⁶ = 28156717 is a prime.

It is a super-2 number, since 2×28156781² = 1585608632563922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28156721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14078390 + 14078391.

It is an arithmetic number, because the mean of its divisors is an integer number (14078391).

Almost surely, 2^28156781 is an apocalyptic number.

It is an amenable number.

28156781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28156781 is an equidigital number, since it uses as much as digits as its factorization.

28156781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 26880, while the sum is 38.

The square root of 28156781 is about 5306.2963543323. The cubic root of 28156781 is about 304.2246038965.

The spelling of 28156781 in words is "twenty-eight million, one hundred fifty-six thousand, seven hundred eighty-one".