991087378 has 4 divisors (see below), whose sum is σ = 1486631070. Its totient is φ = 495543688.

The previous prime is 991087343. The next prime is 991087381. The reversal of 991087378 is 873780199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 873780199 = 8291 ⋅105389.

It can be written as a sum of positive squares in only one way, i.e., 977375169 + 13712209 = 31263^2 + 3703^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 247771843 + ... + 247771846.

Almost surely, 2^991087378 is an apocalyptic number.

991087378 is a deficient number, since it is larger than the sum of its proper divisors (495543692).

991087378 is a wasteful number, since it uses less digits than its factorization.

991087378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495543691.

The product of its (nonzero) digits is 762048, while the sum is 52.

The square root of 991087378 is about 31481.5402736270. The cubic root of 991087378 is about 997.0202559443.

The spelling of 991087378 in words is "nine hundred ninety-one million, eighty-seven thousand, three hundred seventy-eight".