21738281646821 has 16 divisors (see below), whose sum is σ = 23552558409600. Its totient is φ = 19983522037248.

The previous prime is 21738281646743. The next prime is 21738281646827. The reversal of 21738281646821 is 12864618283712.

It is a cyclic number.

It is not a de Polignac number, because 21738281646821 - 2²² = 21738277452517 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21738281646827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 111628025 + ... + 111822593.

It is an arithmetic number, because the mean of its divisors is an integer number (1472034900600).

Almost surely, 2^{21738281646821} is an apocalyptic number.

It is an amenable number.

21738281646821 is a deficient number, since it is larger than the sum of its proper divisors (1814276762779).

21738281646821 is a wasteful number, since it uses less digits than its factorization.

21738281646821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347468.

The product of its digits is 12386304, while the sum is 59.

The spelling of 21738281646821 in words is "twenty-one trillion, seven hundred thirty-eight billion, two hundred eighty-one million, six hundred forty-six thousand, eight hundred twenty-one".