28153781 has 4 divisors (see below), whose sum is σ = 28914732. Its totient is φ = 27392832.

The previous prime is 28153747. The next prime is 28153787. The reversal of 28153781 is 18735182.

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

It can be written as a sum of positive squares in 2 ways, for example, as 27133681 + 1020100 = 5209^2 + 1010^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28153781 is a prime.

It is a super-2 number, since 2×28153781² = 1585270769191922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28153787) 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, 380420 + ... + 380493.

It is an arithmetic number, because the mean of its divisors is an integer number (7228683).

Almost surely, 2^28153781 is an apocalyptic number.

It is an amenable number.

28153781 is a deficient number, since it is larger than the sum of its proper divisors (760951).

28153781 is an equidigital number, since it uses as much as digits as its factorization.

28153781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 760950.

The product of its digits is 13440, while the sum is 35.

The square root of 28153781 is about 5306.0136637593. The cubic root of 28153781 is about 304.2137988471.

The spelling of 28153781 in words is "twenty-eight million, one hundred fifty-three thousand, seven hundred eighty-one".