2161651646421 has 12 divisors (see below), whose sum is σ = 3122398770348. Its totient is φ = 1441095070464.

The previous prime is 2161651646369. The next prime is 2161651646431. The reversal of 2161651646421 is 1246461561612.

2161651646421 is a `hidden beast` number, since 2 + 1 + 6 + 1 + 65 + 164 + 6 + 421 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1837418204196 + 324233442225 = 1355514^2 + 569415^2 .

It is not a de Polignac number, because 2161651646421 - 2¹⁷ = 2161651515349 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2161651646431) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3224901 + ... + 3837093.

It is an arithmetic number, because the mean of its divisors is an integer number (260199897529).

Almost surely, 2^{2161651646421} is an apocalyptic number.

It is an amenable number.

2161651646421 is a deficient number, since it is larger than the sum of its proper divisors (960747123927).

2161651646421 is a wasteful number, since it uses less digits than its factorization.

2161651646421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1004532 (or 1004529 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The spelling of 2161651646421 in words is "two trillion, one hundred sixty-one billion, six hundred fifty-one million, six hundred forty-six thousand, four hundred twenty-one".