991844987 has 4 divisors (see below), whose sum is σ = 1133537136. Its totient is φ = 850152840.

The previous prime is 991844951. The next prime is 991844993. The reversal of 991844987 is 789448199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991844987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991844687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70846064 + ... + 70846077.

It is an arithmetic number, because the mean of its divisors is an integer number (283384284).

Almost surely, 2^991844987 is an apocalyptic number.

991844987 is a deficient number, since it is larger than the sum of its proper divisors (141692149).

991844987 is a wasteful number, since it uses less digits than its factorization.

991844987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141692148.

The product of its digits is 5225472, while the sum is 59.

The square root of 991844987 is about 31493.5705660695. The cubic root of 991844987 is about 997.2742393126.

The spelling of 991844987 in words is "nine hundred ninety-one million, eight hundred forty-four thousand, nine hundred eighty-seven".