990078781 has 2 divisors, whose sum is σ = 990078782. Its totient is φ = 990078780.

The previous prime is 990078773. The next prime is 990078839. The reversal of 990078781 is 187870099.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 561216100 + 428862681 = 23690^2 + 20709^2 .

It is a cyclic number.

It is not a de Polignac number, because 990078781 - 2³ = 990078773 is a prime.

It is a super-2 number, since 2×990078781² = 1960511985172891922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (990078731) 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, 495039390 + 495039391.

It is an arithmetic number, because the mean of its divisors is an integer number (495039391).

Almost surely, 2^990078781 is an apocalyptic number.

It is an amenable number.

990078781 is a deficient number, since it is larger than the sum of its proper divisors (1).

990078781 is an equidigital number, since it uses as much as digits as its factorization.

990078781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 990078781 is about 31465.5173324705. The cubic root of 990078781 is about 996.6819295856.

The spelling of 990078781 in words is "nine hundred ninety million, seventy-eight thousand, seven hundred eighty-one".