991566971 has 4 divisors (see below), whose sum is σ = 1014626712. Its totient is φ = 968507232.

The previous prime is 991566949. The next prime is 991566991. The reversal of 991566971 is 179665199.

It is a happy number.

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

It is not a de Polignac number, because 991566971 - 2⁶ = 991566907 is a prime.

It is a super-2 number, since 2×991566971² = 1966410115956229682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991566911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11529806 + ... + 11529891.

It is an arithmetic number, because the mean of its divisors is an integer number (253656678).

Almost surely, 2^991566971 is an apocalyptic number.

991566971 is a deficient number, since it is larger than the sum of its proper divisors (23059741).

991566971 is a wasteful number, since it uses less digits than its factorization.

991566971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23059740.

The product of its digits is 918540, while the sum is 53.

The square root of 991566971 is about 31489.1564034351. The cubic root of 991566971 is about 997.1810513286.

The spelling of 991566971 in words is "nine hundred ninety-one million, five hundred sixty-six thousand, nine hundred seventy-one".