21346821 has 24 divisors (see below), whose sum is σ = 32314464. Its totient is φ = 14081040.

The previous prime is 21346777. The next prime is 21346837. The reversal of 21346821 is 12864312.

It is not a de Polignac number, because 21346821 - 2⁹ = 21346309 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21346621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25591 + ... + 26411.

It is an arithmetic number, because the mean of its divisors is an integer number (1346436).

Almost surely, 2^21346821 is an apocalyptic number.

It is an amenable number.

21346821 is a deficient number, since it is larger than the sum of its proper divisors (10967643).

21346821 is an equidigital number, since it uses as much as digits as its factorization.

21346821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 943 (or 931 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21346821 is about 4620.2620055577. The cubic root of 21346821 is about 277.4029463377.

The spelling of 21346821 in words is "twenty-one million, three hundred forty-six thousand, eight hundred twenty-one".