991655557 has 8 divisors (see below), whose sum is σ = 1037481984. Its totient is φ = 946055088.

The previous prime is 991655503. The next prime is 991655573. The reversal of 991655557 is 755556199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 991655557 - 2¹⁵ = 991622789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991655597) 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 7 ways as a sum of consecutive naturals, for example, 47478 + ... + 65095.

It is an arithmetic number, because the mean of its divisors is an integer number (129685248).

Almost surely, 2^991655557 is an apocalyptic number.

It is an amenable number.

991655557 is a deficient number, since it is larger than the sum of its proper divisors (45826427).

991655557 is a wasteful number, since it uses less digits than its factorization.

991655557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112979.

The product of its digits is 2126250, while the sum is 52.

The square root of 991655557 is about 31490.5629832177. The cubic root of 991655557 is about 997.2107462972.

The spelling of 991655557 in words is "nine hundred ninety-one million, six hundred fifty-five thousand, five hundred fifty-seven".