2161561251660 has 48 divisors (see below), whose sum is σ = 6063237615456. Its totient is φ = 575381466112.

The previous prime is 2161561251659. The next prime is 2161561251679. The reversal of 2161561251660 is 661521651612.

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, 32305917 + ... + 32372756.

It is an arithmetic number, because the mean of its divisors is an integer number (126317450322).

Almost surely, 2^{2161561251660} is an apocalyptic number.

2161561251660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2161561251660 is an abundant number, since it is smaller than the sum of its proper divisors (3901676363796).

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

2161561251660 is a wasteful number, since it uses less digits than its factorization.

2161561251660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64679242 (or 64679240 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 42.

The spelling of 2161561251660 in words is "two trillion, one hundred sixty-one billion, five hundred sixty-one million, two hundred fifty-one thousand, six hundred sixty".