991663138 has 8 divisors (see below), whose sum is σ = 1487844288. Its totient is φ = 495715044.

The previous prime is 991663121. The next prime is 991663139. The reversal of 991663138 is 831366199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (991663139) 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, 47206 + ... + 64897.

It is an arithmetic number, because the mean of its divisors is an integer number (185980536).

Almost surely, 2^991663138 is an apocalyptic number.

991663138 is a deficient number, since it is larger than the sum of its proper divisors (496181150).

991663138 is a wasteful number, since it uses less digits than its factorization.

991663138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116528.

The product of its digits is 209952, while the sum is 46.

The square root of 991663138 is about 31490.6833523822. The cubic root of 991663138 is about 997.2132874468.

The spelling of 991663138 in words is "nine hundred ninety-one million, six hundred sixty-three thousand, one hundred thirty-eight".