1991507988 has 12 divisors (see below), whose sum is σ = 4646852000. Its totient is φ = 663835992.

The previous prime is 1991507941. The next prime is 1991508031. The reversal of 1991507988 is 8897051991.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×1991507988² = 7932208132535616288, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82979488 + ... + 82979511.

Almost surely, 2^1991507988 is an apocalyptic number.

It is an amenable number.

1991507988 is an abundant number, since it is smaller than the sum of its proper divisors (2655344012).

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

1991507988 is a wasteful number, since it uses less digits than its factorization.

1991507988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165959006 (or 165959004 counting only the distinct ones).

The product of its (nonzero) digits is 1632960, while the sum is 57.

The square root of 1991507988 is about 44626.3149722224. The cubic root of 1991507988 is about 1258.1353093041.

The spelling of 1991507988 in words is "one billion, nine hundred ninety-one million, five hundred seven thousand, nine hundred eighty-eight".