1991065428 has 48 divisors (see below), whose sum is σ = 5631299520. Its totient is φ = 603352800.

The previous prime is 1991065409. The next prime is 1991065501. The reversal of 1991065428 is 8245601991.

1991065428 is a `hidden beast` number, since 1 + 99 + 10 + 6 + 542 + 8 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 836803 + ... + 839178.

It is an arithmetic number, because the mean of its divisors is an integer number (117318740).

Almost surely, 2^1991065428 is an apocalyptic number.

1991065428 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1991065428 is an abundant number, since it is smaller than the sum of its proper divisors (3640234092).

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

1991065428 is a wasteful number, since it uses less digits than its factorization.

1991065428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1676005 (or 1675997 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 45.

The square root of 1991065428 is about 44621.3561873684. The cubic root of 1991065428 is about 1258.0421066297.

The spelling of 1991065428 in words is "one billion, nine hundred ninety-one million, sixty-five thousand, four hundred twenty-eight".