21340021 has 16 divisors (see below), whose sum is σ = 23961600. Its totient is φ = 18908208.

The previous prime is 21340019. The next prime is 21340051. The reversal of 21340021 is 12004312.

It is not a de Polignac number, because 21340021 - 2¹ = 21340019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21339983 and 21340010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21340051) 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, 20020 + ... + 21058.

It is an arithmetic number, because the mean of its divisors is an integer number (1497600).

Almost surely, 2^21340021 is an apocalyptic number.

It is an amenable number.

21340021 is a deficient number, since it is larger than the sum of its proper divisors (2621579).

21340021 is a wasteful number, since it uses less digits than its factorization.

21340021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1128.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21340021 is about 4619.5260579414. The cubic root of 21340021 is about 277.3734877692.

Adding to 21340021 its reverse (12004312), we get a palindrome (33344333).

The spelling of 21340021 in words is "twenty-one million, three hundred forty thousand, twenty-one".