90809981 has 2 divisors, whose sum is σ = 90809982. Its totient is φ = 90809980.

The previous prime is 90809977. The next prime is 90810001. The reversal of 90809981 is 18990809.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50993881 + 39816100 = 7141^2 + 6310^2 .

It is an emirp because it is prime and its reverse (18990809) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 90809981 - 2² = 90809977 is a prime.

It is a super-2 number, since 2×90809981² = 16492905298440722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90809941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45404990 + 45404991.

It is an arithmetic number, because the mean of its divisors is an integer number (45404991).

Almost surely, 2^90809981 is an apocalyptic number.

It is an amenable number.

90809981 is a deficient number, since it is larger than the sum of its proper divisors (1).

90809981 is an equidigital number, since it uses as much as digits as its factorization.

90809981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 44.

The square root of 90809981 is about 9529.4271076492. The cubic root of 90809981 is about 449.4808515135.

The spelling of 90809981 in words is "ninety million, eight hundred nine thousand, nine hundred eighty-one".