989909991 has 40 divisors (see below), whose sum is σ = 1721944224. Its totient is φ = 554973120.

The previous prime is 989909981. The next prime is 989909993. The reversal of 989909991 is 199909989.

It is not a de Polignac number, because 989909991 - 2⁶ = 989909927 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (989909993) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 13581 + ... + 46521.

Almost surely, 2^989909991 is an apocalyptic number.

989909991 is a deficient number, since it is larger than the sum of its proper divisors (732034233).

989909991 is a wasteful number, since it uses less digits than its factorization.

989909991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33013 (or 33004 counting only the distinct ones).

The product of its (nonzero) digits is 4251528, while the sum is 63.

The square root of 989909991 is about 31462.8350756889. The cubic root of 989909991 is about 996.6252877954.

It can be divided in two parts, 9899099 and 91, that multiplied together give a palindrome (900818009).

The spelling of 989909991 in words is "nine hundred eighty-nine million, nine hundred nine thousand, nine hundred ninety-one".