2001561500 has 96 divisors (see below), whose sum is σ = 4538806272. Its totient is φ = 770280000.

The previous prime is 2001561491. The next prime is 2001561503. The reversal of 2001561500 is 51651002.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2001561503) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 4076255 + ... + 4076745.

It is an arithmetic number, because the mean of its divisors is an integer number (47279232).

Almost surely, 2^2001561500 is an apocalyptic number.

2001561500 is a gapful number since it is divisible by the number (20) 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 2001561500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2269403136).

2001561500 is an abundant number, since it is smaller than the sum of its proper divisors (2537244772).

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

2001561500 is a wasteful number, since it uses less digits than its factorization.

2001561500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804 (or 792 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 2001561500 is about 44738.8142444567. The cubic root of 2001561500 is about 1260.2488590506.

The spelling of 2001561500 in words is "two billion, one million, five hundred sixty-one thousand, five hundred".