991037491 has 4 divisors (see below), whose sum is σ = 1049333832. Its totient is φ = 932741152.

The previous prime is 991037471. The next prime is 991037497. The reversal of 991037491 is 194730199.

It is a happy number.

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-991037491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991037497) 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, 29148145 + ... + 29148178.

It is an arithmetic number, because the mean of its divisors is an integer number (262333458).

Almost surely, 2^991037491 is an apocalyptic number.

991037491 is a deficient number, since it is larger than the sum of its proper divisors (58296341).

991037491 is a wasteful number, since it uses less digits than its factorization.

991037491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58296340.

The product of its (nonzero) digits is 61236, while the sum is 43.

The square root of 991037491 is about 31480.7479421948. The cubic root of 991037491 is about 997.0035271186.

The spelling of 991037491 in words is "nine hundred ninety-one million, thirty-seven thousand, four hundred ninety-one".