991090278 has 48 divisors (see below), whose sum is σ = 2183500800. Its totient is φ = 324829680.

The previous prime is 991090277. The next prime is 991090307. The reversal of 991090278 is 872090199.

It is a super-2 number, since 2×991090278² = 1964519878292234568, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991090271) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 611353 + ... + 612971.

It is an arithmetic number, because the mean of its divisors is an integer number (45489600).

Almost surely, 2^991090278 is an apocalyptic number.

991090278 is an abundant number, since it is smaller than the sum of its proper divisors (1192410522).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991090278 is a wasteful number, since it uses less digits than its factorization.

991090278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2177 (or 2174 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 991090278 is about 31481.5863323308. The cubic root of 991090278 is about 997.0212283967.

The spelling of 991090278 in words is "nine hundred ninety-one million, ninety thousand, two hundred seventy-eight".