991994689 has 4 divisors (see below), whose sum is σ = 1133708224. Its totient is φ = 850281156.

The previous prime is 991994683. The next prime is 991994711. The reversal of 991994689 is 986499199.

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: 986499199 = 7 ⋅140928457.

It is a cyclic number.

It is not a de Polignac number, because 991994689 - 2⁵ = 991994657 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991994689.

It is not an unprimeable number, because it can be changed into a prime (991994683) 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, 70856757 + ... + 70856770.

It is an arithmetic number, because the mean of its divisors is an integer number (283427056).

Almost surely, 2^991994689 is an apocalyptic number.

It is an amenable number.

991994689 is a deficient number, since it is larger than the sum of its proper divisors (141713535).

991994689 is a wasteful number, since it uses less digits than its factorization.

991994689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141713534.

The product of its digits is 11337408, while the sum is 64.

The square root of 991994689 is about 31495.9471837251. The cubic root of 991994689 is about 997.3244106060.

The spelling of 991994689 in words is "nine hundred ninety-one million, nine hundred ninety-four thousand, six hundred eighty-nine".