91987789 has 4 divisors (see below), whose sum is σ = 93945024. Its totient is φ = 90030556.

The previous prime is 91987783. The next prime is 91987801. The reversal of 91987789 is 98778919.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 91987789 - 2¹³ = 91979597 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 (91987783) 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, 978547 + ... + 978640.

It is an arithmetic number, because the mean of its divisors is an integer number (23486256).

Almost surely, 2^91987789 is an apocalyptic number.

It is an amenable number.

91987789 is a deficient number, since it is larger than the sum of its proper divisors (1957235).

91987789 is a wasteful number, since it uses less digits than its factorization.

91987789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1957234.

The product of its digits is 2286144, while the sum is 58.

The square root of 91987789 is about 9591.0264831247. The cubic root of 91987789 is about 451.4157699033.

The spelling of 91987789 in words is "ninety-one million, nine hundred eighty-seven thousand, seven hundred eighty-nine".