90691781 has 2 divisors, whose sum is σ = 90691782. Its totient is φ = 90691780.

The previous prime is 90691759. The next prime is 90691789. The reversal of 90691781 is 18719609.

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., 56761156 + 33930625 = 7534^2 + 5825^2 .

It is a cyclic number.

It is not a de Polignac number, because 90691781 - 2¹⁴ = 90675397 is a prime.

It is a super-2 number, since 2×90691781² = 16449998281903922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90691789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45345890 + 45345891.

It is an arithmetic number, because the mean of its divisors is an integer number (45345891).

Almost surely, 2^90691781 is an apocalyptic number.

It is an amenable number.

90691781 is a deficient number, since it is larger than the sum of its proper divisors (1).

90691781 is an equidigital number, since it uses as much as digits as its factorization.

90691781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27216, while the sum is 41.

The square root of 90691781 is about 9523.2232463594. The cubic root of 90691781 is about 449.2857492284.

The spelling of 90691781 in words is "ninety million, six hundred ninety-one thousand, seven hundred eighty-one".