42021509 has 2 divisors, whose sum is σ = 42021510. Its totient is φ = 42021508.

The previous prime is 42021401. The next prime is 42021517. The reversal of 42021509 is 90512024.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 39413284 + 2608225 = 6278^2 + 1615^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42021509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42021589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21010754 + 21010755.

It is an arithmetic number, because the mean of its divisors is an integer number (21010755).

Almost surely, 2^42021509 is an apocalyptic number.

It is an amenable number.

42021509 is a deficient number, since it is larger than the sum of its proper divisors (1).

42021509 is an equidigital number, since it uses as much as digits as its factorization.

42021509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 42021509 is about 6482.3999413797. The cubic root of 42021509 is about 347.6619923440.

The spelling of 42021509 in words is "forty-two million, twenty-one thousand, five hundred nine".