2181815280821 has 8 divisors (see below), whose sum is σ = 2456941548288. Its totient is φ = 1919485584000.

The previous prime is 2181815280811. The next prime is 2181815280871. The reversal of 2181815280821 is 1280825181812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2181815280821 - 2²² = 2181811086517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181815280811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3199142300 + ... + 3199142981.

It is an arithmetic number, because the mean of its divisors is an integer number (307117693536).

Almost surely, 2^{2181815280821} is an apocalyptic number.

It is an amenable number.

2181815280821 is a deficient number, since it is larger than the sum of its proper divisors (275126267467).

2181815280821 is a wasteful number, since it uses less digits than its factorization.

2181815280821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6398285323.

The product of its (nonzero) digits is 163840, while the sum is 47.

Subtracting from 2181815280821 its reverse (1280825181812), we obtain a palindrome (900990099009).

The spelling of 2181815280821 in words is "two trillion, one hundred eighty-one billion, eight hundred fifteen million, two hundred eighty thousand, eight hundred twenty-one".