55991000 has 128 divisors (see below), whose sum is σ = 145454400. Its totient is φ = 20044800.

The previous prime is 55990999. The next prime is 55991003. The reversal of 55991000 is 19955.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55991003) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 766964 + ... + 767036.

Almost surely, 2^55991000 is an apocalyptic number.

55991000 is a gapful number since it is divisible by the number (50) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 55991000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (72727200).

55991000 is an abundant number, since it is smaller than the sum of its proper divisors (89463400).

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

55991000 is a wasteful number, since it uses less digits than its factorization.

55991000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 2025, while the sum is 29.

The square root of 55991000 is about 7482.7134115907. The cubic root of 55991000 is about 382.5657397652.

The spelling of 55991000 in words is "fifty-five million, nine hundred ninety-one thousand".