90987781 has 2 divisors, whose sum is σ = 90987782. Its totient is φ = 90987780.

The previous prime is 90987749. The next prime is 90987797. The reversal of 90987781 is 18778909.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54626881 + 36360900 = 7391^2 + 6030^2 .

It is a cyclic number.

It is not a de Polignac number, because 90987781 - 2⁵ = 90987749 is a prime.

It is a super-2 number, since 2×90987781² = 16557552582607922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90987881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45493890 + 45493891.

It is an arithmetic number, because the mean of its divisors is an integer number (45493891).

Almost surely, 2^90987781 is an apocalyptic number.

It is an amenable number.

90987781 is a deficient number, since it is larger than the sum of its proper divisors (1).

90987781 is an equidigital number, since it uses as much as digits as its factorization.

90987781 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 90987781 is about 9538.7515430480. The cubic root of 90987781 is about 449.7740116313.

The spelling of 90987781 in words is "ninety million, nine hundred eighty-seven thousand, seven hundred eighty-one".