90181991 has 16 divisors (see below), whose sum is σ = 98350848. Its totient is φ = 82368000.

The previous prime is 90181979. The next prime is 90182003. The reversal of 90181991 is 19918109.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (90181979) and next prime (90182003).

It is a cyclic number.

It is not a de Polignac number, because 90181991 - 2¹⁰ = 90180967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90181901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 90506 + ... + 91496.

It is an arithmetic number, because the mean of its divisors is an integer number (6146928).

Almost surely, 2^90181991 is an apocalyptic number.

90181991 is a deficient number, since it is larger than the sum of its proper divisors (8168857).

90181991 is a wasteful number, since it uses less digits than its factorization.

90181991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1162.

The product of its (nonzero) digits is 5832, while the sum is 38.

The square root of 90181991 is about 9496.4199043640. The cubic root of 90181991 is about 448.4423362176.

The spelling of 90181991 in words is "ninety million, one hundred eighty-one thousand, nine hundred ninety-one".