21244340021 has 16 divisors (see below), whose sum is σ = 23879846400. Its totient is φ = 18805348800.

The previous prime is 21244339999. The next prime is 21244340023. The reversal of 21244340021 is 12004344212.

It is not a de Polignac number, because 21244340021 - 2²⁶ = 21177231157 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 (21244340023) 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, 604790 + ... + 638951.

It is an arithmetic number, because the mean of its divisors is an integer number (1492490400).

Almost surely, 2^21244340021 is an apocalyptic number.

It is an amenable number.

21244340021 is a deficient number, since it is larger than the sum of its proper divisors (2635506379).

21244340021 is a wasteful number, since it uses less digits than its factorization.

21244340021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1243820.

The product of its (nonzero) digits is 1536, while the sum is 23.

Adding to 21244340021 its reverse (12004344212), we get a palindrome (33248684233).

The spelling of 21244340021 in words is "twenty-one billion, two hundred forty-four million, three hundred forty thousand, twenty-one".