42172809 has 16 divisors (see below), whose sum is σ = 65759232. Its totient is φ = 23537808.

The previous prime is 42172783. The next prime is 42172813. The reversal of 42172809 is 90827124.

It is a happy number.

It is not a de Polignac number, because 42172809 - 2⁹ = 42172297 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 42172809.

It is not an unprimeable number, because it can be changed into a prime (42172849) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22449 + ... + 24254.

It is an arithmetic number, because the mean of its divisors is an integer number (4109952).

Almost surely, 2^42172809 is an apocalyptic number.

It is an amenable number.

42172809 is a deficient number, since it is larger than the sum of its proper divisors (23586423).

42172809 is a wasteful number, since it uses less digits than its factorization.

42172809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46756.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 42172809 is about 6494.0595162040. The cubic root of 42172809 is about 348.0787491886.

The spelling of 42172809 in words is "forty-two million, one hundred seventy-two thousand, eight hundred nine".