331666991 has 4 divisors (see below), whose sum is σ = 351176832. Its totient is φ = 312157152.

The previous prime is 331666961. The next prime is 331667003. The reversal of 331666991 is 199666133.

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

It is a cyclic number.

It is not a de Polignac number, because 331666991 - 2²² = 327472687 is a prime.

It is a super-2 number, since 2×331666991² = 220005985837988162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (331666961) 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, 9754895 + ... + 9754928.

It is an arithmetic number, because the mean of its divisors is an integer number (87794208).

Almost surely, 2^331666991 is an apocalyptic number.

331666991 is a deficient number, since it is larger than the sum of its proper divisors (19509841).

331666991 is a wasteful number, since it uses less digits than its factorization.

331666991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19509840.

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

The square root of 331666991 is about 18211.7267440515. The cubic root of 331666991 is about 692.2039664881.

It can be divided in two parts, 3316 and 66991, that added together give a palindrome (70307).

The spelling of 331666991 in words is "three hundred thirty-one million, six hundred sixty-six thousand, nine hundred ninety-one".