91990 has 8 divisors (see below), whose sum is σ = 165600. Its totient is φ = 36792.

The previous prime is 91969. The next prime is 91997. The reversal of 91990 is 9919.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91997) 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, 4590 + ... + 4609.

It is an arithmetic number, because the mean of its divisors is an integer number (20700).

2⁹¹⁹⁹⁰ is an apocalyptic number.

91990 is a deficient number, since it is larger than the sum of its proper divisors (73610).

91990 is a wasteful number, since it uses less digits than its factorization.

91990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9206.

The product of its (nonzero) digits is 729, while the sum is 28.

The square root of 91990 is about 303.2985328023. The cubic root of 91990 is about 45.1419386587.

It can be divided in two parts, 91 and 990, that added together give a triangular number (1081 = T₄₆).

The spelling of 91990 in words is "ninety-one thousand, nine hundred ninety".