1991445690 has 64 divisors (see below), whose sum is σ = 5224012416. Its totient is φ = 482879232.

The previous prime is 1991445679. The next prime is 1991445697. The reversal of 1991445690 is 965441991.

It is a happy number.

It is a super-2 number, since 2×1991445690² = 7931711872439152200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1991445697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 11977 + ... + 64236.

It is an arithmetic number, because the mean of its divisors is an integer number (81625194).

Almost surely, 2^1991445690 is an apocalyptic number.

1991445690 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1991445690 is an abundant number, since it is smaller than the sum of its proper divisors (3232566726).

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

1991445690 is a wasteful number, since it uses less digits than its factorization.

1991445690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76303.

The product of its (nonzero) digits is 349920, while the sum is 48.

The square root of 1991445690 is about 44625.6169705249. The cubic root of 1991445690 is about 1258.1221902454.

The spelling of 1991445690 in words is "one billion, nine hundred ninety-one million, four hundred forty-five thousand, six hundred ninety".