42556781 has 2 divisors, whose sum is σ = 42556782. Its totient is φ = 42556780.

The previous prime is 42556757. The next prime is 42556823. The reversal of 42556781 is 18765524.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 42445225 + 111556 = 6515^2 + 334^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42556781 is a prime.

It is a super-2 number, since 2×42556781² = 3622159218163922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42556741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21278390 + 21278391.

It is an arithmetic number, because the mean of its divisors is an integer number (21278391).

Almost surely, 2^42556781 is an apocalyptic number.

It is an amenable number.

42556781 is a deficient number, since it is larger than the sum of its proper divisors (1).

42556781 is an equidigital number, since it uses as much as digits as its factorization.

42556781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 67200, while the sum is 38.

The square root of 42556781 is about 6523.5558555132. Note that the first 3 decimals coincide. The cubic root of 42556781 is about 349.1319468353.

The spelling of 42556781 in words is "forty-two million, five hundred fifty-six thousand, seven hundred eighty-one".