2161561020 has 48 divisors (see below), whose sum is σ = 6181152768. Its totient is φ = 564151360.

The previous prime is 2161561019. The next prime is 2161561057. The reversal of 2161561020 is 201651612.

2161561020 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 380436 + ... + 386075.

It is an arithmetic number, because the mean of its divisors is an integer number (128774016).

Almost surely, 2^2161561020 is an apocalyptic number.

2161561020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2161561020 is an abundant number, since it is smaller than the sum of its proper divisors (4019591748).

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

2161561020 is a wasteful number, since it uses less digits than its factorization.

2161561020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 766570 (or 766568 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 24.

The square root of 2161561020 is about 46492.5910226565. The cubic root of 2161561020 is about 1292.9721386299.

The spelling of 2161561020 in words is "two billion, one hundred sixty-one million, five hundred sixty-one thousand, twenty".