1991409588 has 54 divisors (see below), whose sum is σ = 5855697666. Its totient is φ = 568973664.

The previous prime is 1991409587. The next prime is 1991409601. The reversal of 1991409588 is 8859041991.

1991409588 is a `hidden beast` number, since 19 + 9 + 1 + 40 + 9 + 588 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1512587664 + 478821924 = 38892^2 + 21882^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991409587) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 562695 + ... + 566222.

Almost surely, 2^1991409588 is an apocalyptic number.

1991409588 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1991409588 is an abundant number, since it is smaller than the sum of its proper divisors (3864288078).

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

1991409588 is a wasteful number, since it uses less digits than its factorization.

1991409588 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1128941 (or 1128929 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 54.

The square root of 1991409588 is about 44625.2124700824. The cubic root of 1991409588 is about 1258.1145875606.

The spelling of 1991409588 in words is "one billion, nine hundred ninety-one million, four hundred nine thousand, five hundred eighty-eight".