21540445400021 has 12 divisors (see below), whose sum is σ = 21703468982400. Its totient is φ = 21377978964048.

The previous prime is 21540445399969. The next prime is 21540445400053. The reversal of 21540445400021 is 12000454404512.

It is not a de Polignac number, because 21540445400021 - 2¹⁴ = 21540445383637 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 (21540445400081) 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, 46143260 + ... + 46607738.

It is an arithmetic number, because the mean of its divisors is an integer number (1808622415200).

Almost surely, 2^{21540445400021} is an apocalyptic number.

It is an amenable number.

21540445400021 is a deficient number, since it is larger than the sum of its proper divisors (163023582379).

21540445400021 is an frugal number, since it uses more digits than its factorization.

21540445400021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 465676 (or 465167 counting only the distinct ones).

The product of its (nonzero) digits is 25600, while the sum is 32.

Adding to 21540445400021 its reverse (12000454404512), we get a palindrome (33540899804533).

The spelling of 21540445400021 in words is "twenty-one trillion, five hundred forty billion, four hundred forty-five million, four hundred thousand, twenty-one".