990438781 has 2 divisors, whose sum is σ = 990438782. Its totient is φ = 990438780.

The previous prime is 990438671. The next prime is 990438791. The reversal of 990438781 is 187834099.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 580376281 + 410062500 = 24091^2 + 20250^2 .

It is a cyclic number.

It is not a de Polignac number, because 990438781 - 2⁹ = 990438269 is a prime.

It is a super-2 number, since 2×990438781² = 1961937957817531922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (990438791) 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, 495219390 + 495219391.

It is an arithmetic number, because the mean of its divisors is an integer number (495219391).

Almost surely, 2^990438781 is an apocalyptic number.

It is an amenable number.

990438781 is a deficient number, since it is larger than the sum of its proper divisors (1).

990438781 is an equidigital number, since it uses as much as digits as its factorization.

990438781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 435456, while the sum is 49.

The square root of 990438781 is about 31471.2373604852. The cubic root of 990438781 is about 996.8027152652.

The spelling of 990438781 in words is "nine hundred ninety million, four hundred thirty-eight thousand, seven hundred eighty-one".