21526821 has 12 divisors (see below), whose sum is σ = 31181280. Its totient is φ = 14311080.

The previous prime is 21526793. The next prime is 21526823. The reversal of 21526821 is 12862512.

It is a happy number.

It is not a de Polignac number, because 21526821 - 2⁷ = 21526693 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21526823) 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 11 ways as a sum of consecutive naturals, for example, 256 + ... + 6566.

It is an arithmetic number, because the mean of its divisors is an integer number (2598440).

Almost surely, 2^21526821 is an apocalyptic number.

It is an amenable number.

21526821 is a deficient number, since it is larger than the sum of its proper divisors (9654459).

21526821 is a wasteful number, since it uses less digits than its factorization.

21526821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6696 (or 6693 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21526821 is about 4639.7005291290. The cubic root of 21526821 is about 278.1804678496.

The spelling of 21526821 in words is "twenty-one million, five hundred twenty-six thousand, eight hundred twenty-one".