42728809 has 4 divisors (see below), whose sum is σ = 43269760. Its totient is φ = 42187860.

The previous prime is 42728789. The next prime is 42728827. The reversal of 42728809 is 90882724.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42728809 is a prime.

It is a super-2 number, since 2×42728809² = 3651502237116962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (42728899) 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, 270357 + ... + 270514.

It is an arithmetic number, because the mean of its divisors is an integer number (10817440).

Almost surely, 2^42728809 is an apocalyptic number.

It is an amenable number.

42728809 is a deficient number, since it is larger than the sum of its proper divisors (540951).

42728809 is an equidigital number, since it uses as much as digits as its factorization.

42728809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540950.

The product of its (nonzero) digits is 64512, while the sum is 40.

The square root of 42728809 is about 6536.7276981683. The cubic root of 42728809 is about 349.6017483771.

The spelling of 42728809 in words is "forty-two million, seven hundred twenty-eight thousand, eight hundred nine".