90605991 has 32 divisors (see below), whose sum is σ = 142000128. Its totient is φ = 50319360.

The previous prime is 90605987. The next prime is 90606071. The reversal of 90605991 is 19950609.

90605991 is a nontrivial binomial coefficient, being equal to C(13462, 2).

It is not a de Polignac number, because 90605991 - 2² = 90605987 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90605791) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 141031 + ... + 141671.

It is an arithmetic number, because the mean of its divisors is an integer number (4437504).

Almost surely, 2^90605991 is an apocalyptic number.

90605991 is the 13461-st triangular number and also the 6731-st hexagonal number.

90605991 is a deficient number, since it is larger than the sum of its proper divisors (51394137).

90605991 is a wasteful number, since it uses less digits than its factorization.

90605991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 831.

The product of its (nonzero) digits is 21870, while the sum is 39.

The square root of 90605991 is about 9518.7179283767. The cubic root of 90605991 is about 449.1440370687.

It can be divided in two parts, 9060 and 5991, that added together give a palindrome (15051).

The spelling of 90605991 in words is "ninety million, six hundred five thousand, nine hundred ninety-one".