42009391 has 2 divisors, whose sum is σ = 42009392. Its totient is φ = 42009390.

The previous prime is 42009353. The next prime is 42009403. The reversal of 42009391 is 19390024.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 42009391 - 2¹³ = 42001199 is a prime.

It is equal to p_2548144 and since 42009391 and 2548144 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 (42009311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21004695 + 21004696.

It is an arithmetic number, because the mean of its divisors is an integer number (21004696).

Almost surely, 2^42009391 is an apocalyptic number.

42009391 is a deficient number, since it is larger than the sum of its proper divisors (1).

42009391 is an equidigital number, since it uses as much as digits as its factorization.

42009391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 42009391 is about 6481.4651892917. The cubic root of 42009391 is about 347.6285699915.

The spelling of 42009391 in words is "forty-two million, nine thousand, three hundred ninety-one".