90090991991 has 16 divisors (see below), whose sum is σ = 120961333248. Its totient is φ = 64800712800.

The previous prime is 90090991979. The next prime is 90090991997. The reversal of 90090991991 is 19919909009.

It is a cyclic number.

It is not a de Polignac number, because 90090991991 - 2¹⁸ = 90090729847 is a prime.

It is a super-3 number, since 3×90090991991³ (a number of 34 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90090991997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44999495 + ... + 45001496.

It is an arithmetic number, because the mean of its divisors is an integer number (7560083328).

Almost surely, 2^90090991991 is an apocalyptic number.

90090991991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

90090991991 is a deficient number, since it is larger than the sum of its proper divisors (30870341257).

90090991991 is a wasteful number, since it uses less digits than its factorization.

90090991991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90001022.

The product of its (nonzero) digits is 531441, while the sum is 56.

The spelling of 90090991991 in words is "ninety billion, ninety million, nine hundred ninety-one thousand, nine hundred ninety-one".