2121378064181 has 4 divisors (see below), whose sum is σ = 2121381840492. Its totient is φ = 2121374287872.

The previous prime is 2121378064151. The next prime is 2121378064187. The reversal of 2121378064181 is 1814608731212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1915746651025 + 205631413156 = 1384105^2 + 453466^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2121378064181 is a prime.

It is a super-2 number, since 2×2121378064181² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2121378064187) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 858266 + ... + 2231451.

It is an arithmetic number, because the mean of its divisors is an integer number (530345460123).

Almost surely, 2^{2121378064181} is an apocalyptic number.

It is an amenable number.

2121378064181 is a deficient number, since it is larger than the sum of its proper divisors (3776311).

2121378064181 is an equidigital number, since it uses as much as digits as its factorization.

2121378064181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3776310.

The product of its (nonzero) digits is 129024, while the sum is 44.

The spelling of 2121378064181 in words is "two trillion, one hundred twenty-one billion, three hundred seventy-eight million, sixty-four thousand, one hundred eighty-one".