491556781 has 2 divisors, whose sum is σ = 491556782. Its totient is φ = 491556780.

The previous prime is 491556761. The next prime is 491556827. The reversal of 491556781 is 187655194.

It is an a-pointer prime, because the next prime (491556827) can be obtained adding 491556781 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 302934025 + 188622756 = 17405^2 + 13734^2 .

It is a cyclic number.

It is not a de Polignac number, because 491556781 - 2²¹ = 489459629 is a prime.

It is a super-2 number, since 2×491556781² = 483256137894163922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (491556761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 245778390 + 245778391.

It is an arithmetic number, because the mean of its divisors is an integer number (245778391).

Almost surely, 2^491556781 is an apocalyptic number.

It is an amenable number.

491556781 is a deficient number, since it is larger than the sum of its proper divisors (1).

491556781 is an equidigital number, since it uses as much as digits as its factorization.

491556781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 302400, while the sum is 46.

The square root of 491556781 is about 22171.0798338737. The cubic root of 491556781 is about 789.2075485696.

The spelling of 491556781 in words is "four hundred ninety-one million, five hundred fifty-six thousand, seven hundred eighty-one".