21526421 has 4 divisors (see below), whose sum is σ = 24601632. Its totient is φ = 18451212.

The previous prime is 21526397. The next prime is 21526429. The reversal of 21526421 is 12462512.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21526421 - 2⁶ = 21526357 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 (21526429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1537595 + ... + 1537608.

It is an arithmetic number, because the mean of its divisors is an integer number (6150408).

Almost surely, 2^21526421 is an apocalyptic number.

It is an amenable number.

21526421 is a deficient number, since it is larger than the sum of its proper divisors (3075211).

21526421 is an equidigital number, since it uses as much as digits as its factorization.

21526421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3075210.

The product of its digits is 960, while the sum is 23.

The square root of 21526421 is about 4639.6574226984. The cubic root of 21526421 is about 278.1787448382.

Adding to 21526421 its reverse (12462512), we get a palindrome (33988933).

The spelling of 21526421 in words is "twenty-one million, five hundred twenty-six thousand, four hundred twenty-one".