42780781 has 2 divisors, whose sum is σ = 42780782. Its totient is φ = 42780780.

The previous prime is 42780779. The next prime is 42780797. The reversal of 42780781 is 18708724.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39576681 + 3204100 = 6291^2 + 1790^2 .

It is a cyclic number.

It is not a de Polignac number, because 42780781 - 2¹ = 42780779 is a prime.

It is a super-2 number, since 2×42780781² = 3660390445939922, which contains 22 as substring.

Together with 42780779, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 42780781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42780181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21390390 + 21390391.

It is an arithmetic number, because the mean of its divisors is an integer number (21390391).

Almost surely, 2^42780781 is an apocalyptic number.

It is an amenable number.

42780781 is a deficient number, since it is larger than the sum of its proper divisors (1).

42780781 is an equidigital number, since it uses as much as digits as its factorization.

42780781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25088, while the sum is 37.

The square root of 42780781 is about 6540.7018736524. The cubic root of 42780781 is about 349.7434337397.

The spelling of 42780781 in words is "forty-two million, seven hundred eighty thousand, seven hundred eighty-one".