991689012 has 18 divisors (see below), whose sum is σ = 2506769538. Its totient is φ = 330562992.

The previous prime is 991689011. The next prime is 991689073. The reversal of 991689012 is 210986199.

It can be written as a sum of positive squares in only one way, i.e., 577729296 + 413959716 = 24036^2 + 20346^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×991689012² = 1966894193043072288, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991689011) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13773423 + ... + 13773494.

Almost surely, 2^991689012 is an apocalyptic number.

It is an amenable number.

991689012 is an abundant number, since it is smaller than the sum of its proper divisors (1515080526).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991689012 is a wasteful number, since it uses less digits than its factorization.

991689012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27546927 (or 27546922 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 45.

The square root of 991689012 is about 31491.0941696220. The cubic root of 991689012 is about 997.2219603087.

The spelling of 991689012 in words is "nine hundred ninety-one million, six hundred eighty-nine thousand, twelve".