42015781 has 2 divisors, whose sum is σ = 42015782. Its totient is φ = 42015780.

The previous prime is 42015749. The next prime is 42015793. The reversal of 42015781 is 18751024.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 30625156 + 11390625 = 5534^2 + 3375^2 .

It is a cyclic number.

It is not a de Polignac number, because 42015781 - 2⁵ = 42015749 is a prime.

It is a super-3 number, since 3×42015781³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is equal to p_2548522 and since 42015781 and 2548522 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 (42015731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21007890 + 21007891.

It is an arithmetic number, because the mean of its divisors is an integer number (21007891).

Almost surely, 2^42015781 is an apocalyptic number.

It is an amenable number.

42015781 is a deficient number, since it is larger than the sum of its proper divisors (1).

42015781 is an equidigital number, since it uses as much as digits as its factorization.

42015781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 42015781 is about 6481.9581146441. The cubic root of 42015781 is about 347.6461948914.

The spelling of 42015781 in words is "forty-two million, fifteen thousand, seven hundred eighty-one".