21340213421 has 4 divisors (see below), whose sum is σ = 21340964700. Its totient is φ = 21339462144.

The previous prime is 21340213381. The next prime is 21340213423. The reversal of 21340213421 is 12431204312.

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 4835672521 + 16504540900 = 69539^2 + 128470^2 .

It is a cyclic number.

It is not a de Polignac number, because 21340213421 - 2¹⁸ = 21339951277 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 (21340213423) 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, 331286 + ... + 390423.

It is an arithmetic number, because the mean of its divisors is an integer number (5335241175).

Almost surely, 2^21340213421 is an apocalyptic number.

It is an amenable number.

21340213421 is a deficient number, since it is larger than the sum of its proper divisors (751279).

21340213421 is an equidigital number, since it uses as much as digits as its factorization.

21340213421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 751278.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21340213421 its reverse (12431204312), we get a palindrome (33771417733).

The spelling of 21340213421 in words is "twenty-one billion, three hundred forty million, two hundred thirteen thousand, four hundred twenty-one".