2155161994209 has 81 divisors (see below), whose sum is σ = 3693673743123. Its totient is φ = 1207368830304.

The previous prime is 2155161994199. The next prime is 2155161994231. The reversal of 2155161994209 is 9024991615512.

It is a happy number.

The square root of 2155161994209 is 1468047.

It is a perfect power (a square), and thus also a powerful number.

2155161994209 is a `hidden beast` number, since 2 + 1 + 5 + 516 + 19 + 94 + 20 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1553650067025 + 601511927184 = 1246455^2 + 775572^2 .

It is not a de Polignac number, because 2155161994209 - 2⁷ = 2155161994081 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2155161994289) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 1633935652 + ... + 1633936970.

Almost surely, 2^{2155161994209} is an apocalyptic number.

2155161994209 is the 1468047-th square number.

2155161994209 is the 734024-th centered octagonal number.

It is an amenable number.

2155161994209 is a deficient number, since it is larger than the sum of its proper divisors (1538511748914).

2155161994209 is an frugal number, since it uses more digits than its factorization.

2155161994209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2764 (or 1382 counting only the distinct ones).

The product of its (nonzero) digits is 1749600, while the sum is 54.

The spelling of 2155161994209 in words is "two trillion, one hundred fifty-five billion, one hundred sixty-one million, nine hundred ninety-four thousand, two hundred nine".