90511991 has 4 divisors (see below), whose sum is σ = 95275800. Its totient is φ = 85748184.

The previous prime is 90511979. The next prime is 90511997. The reversal of 90511991 is 19911509.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 90511991 - 2¹⁰ = 90510967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90511997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2381876 + ... + 2381913.

It is an arithmetic number, because the mean of its divisors is an integer number (23818950).

Almost surely, 2^90511991 is an apocalyptic number.

90511991 is a deficient number, since it is larger than the sum of its proper divisors (4763809).

90511991 is a wasteful number, since it uses less digits than its factorization.

90511991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4763808.

The product of its (nonzero) digits is 3645, while the sum is 35.

The square root of 90511991 is about 9513.7790073136. The cubic root of 90511991 is about 448.9886604842.

The spelling of 90511991 in words is "ninety million, five hundred eleven thousand, nine hundred ninety-one".