991138 has 4 divisors (see below), whose sum is σ = 1486710. Its totient is φ = 495568.

The previous prime is 991129. The next prime is 991147. The reversal of 991138 is 831199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 831199 = 53 ⋅15683.

It is an interprime number because it is at equal distance from previous prime (991129) and next prime (991147).

It can be written as a sum of positive squares in only one way, i.e., 651249 + 339889 = 807^2 + 583^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 247783 + ... + 247786.

2⁹⁹¹¹³⁸ is an apocalyptic number.

991138 is a deficient number, since it is larger than the sum of its proper divisors (495572).

991138 is a wasteful number, since it uses less digits than its factorization.

991138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495571.

The product of its digits is 1944, while the sum is 31.

The square root of 991138 is about 995.5591393785. The cubic root of 991138 is about 99.7037230667.

The spelling of 991138 in words is "nine hundred ninety-one thousand, one hundred thirty-eight".