21342521 has 4 divisors (see below), whose sum is σ = 22078500. Its totient is φ = 20606544.

The previous prime is 21342511. The next prime is 21342523. The reversal of 21342521 is 12524312.

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 3610000 + 17732521 = 1900^2 + 4211^2 .

It is a cyclic number.

It is not a de Polignac number, because 21342521 - 2⁶ = 21342457 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21342493 and 21342502.

It is not an unprimeable number, because it can be changed into a prime (21342523) 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, 367946 + ... + 368003.

It is an arithmetic number, because the mean of its divisors is an integer number (5519625).

Almost surely, 2^21342521 is an apocalyptic number.

It is an amenable number.

21342521 is a deficient number, since it is larger than the sum of its proper divisors (735979).

21342521 is an equidigital number, since it uses as much as digits as its factorization.

21342521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 735978.

The product of its digits is 480, while the sum is 20.

The square root of 21342521 is about 4619.7966405460. The cubic root of 21342521 is about 277.3843188526.

Adding to 21342521 its reverse (12524312), we get a palindrome (33866833).

The spelling of 21342521 in words is "twenty-one million, three hundred forty-two thousand, five hundred twenty-one".