42172309 has 2 divisors, whose sum is σ = 42172310. Its totient is φ = 42172308.

The previous prime is 42172303. The next prime is 42172321. The reversal of 42172309 is 90327124.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 35070084 + 7102225 = 5922^2 + 2665^2 .

It is a cyclic number.

It is not a de Polignac number, because 42172309 - 2¹⁵ = 42139541 is a prime.

It is a Chen prime.

It is equal to p_2557450 and since 42172309 and 2557450 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42172303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21086154 + 21086155.

It is an arithmetic number, because the mean of its divisors is an integer number (21086155).

Almost surely, 2^42172309 is an apocalyptic number.

It is an amenable number.

42172309 is a deficient number, since it is larger than the sum of its proper divisors (1).

42172309 is an equidigital number, since it uses as much as digits as its factorization.

42172309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 42172309 is about 6494.0210193685. The cubic root of 42172309 is about 348.0773735782.

The spelling of 42172309 in words is "forty-two million, one hundred seventy-two thousand, three hundred nine".