991131893 has 4 divisors (see below), whose sum is σ = 1034224608. Its totient is φ = 948039180.

The previous prime is 991131881. The next prime is 991131899. The reversal of 991131893 is 398131199.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 398131199 = 6673 ⋅59663.

It is a cyclic number.

It is not a de Polignac number, because 991131893 - 2⁶ = 991131829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991131899) 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, 21546323 + ... + 21546368.

It is an arithmetic number, because the mean of its divisors is an integer number (258556152).

Almost surely, 2^991131893 is an apocalyptic number.

It is an amenable number.

991131893 is a deficient number, since it is larger than the sum of its proper divisors (43092715).

991131893 is a wasteful number, since it uses less digits than its factorization.

991131893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43092714.

The product of its digits is 52488, while the sum is 44.

The square root of 991131893 is about 31482.2472673092. The cubic root of 991131893 is about 997.0351828798.

The spelling of 991131893 in words is "nine hundred ninety-one million, one hundred thirty-one thousand, eight hundred ninety-three".