991666331 has 4 divisors (see below), whose sum is σ = 992161464. Its totient is φ = 991171200.

The previous prime is 991666327. The next prime is 991666337. The reversal of 991666331 is 133666199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 133666199 = 2003 ⋅66733.

It is a cyclic number.

It is not a de Polignac number, because 991666331 - 2² = 991666327 is a prime.

It is a super-2 number, since 2×991666331² = 1966804224078003122, which contains 22 as substring.

It is a deceptive number, since it divides R_991666330.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991666337) 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, 244550 + ... + 248571.

It is an arithmetic number, because the mean of its divisors is an integer number (248040366).

Almost surely, 2^991666331 is an apocalyptic number.

991666331 is a deficient number, since it is larger than the sum of its proper divisors (495133).

991666331 is a wasteful number, since it uses less digits than its factorization.

991666331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495132.

The product of its digits is 157464, while the sum is 44.

The square root of 991666331 is about 31490.7340498757. The cubic root of 991666331 is about 997.2143577359.

The spelling of 991666331 in words is "nine hundred ninety-one million, six hundred sixty-six thousand, three hundred thirty-one".