21525643 has 2 divisors, whose sum is σ = 21525644. Its totient is φ = 21525642.

The previous prime is 21525641. The next prime is 21525653. The reversal of 21525643 is 34652512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21525643 - 2¹ = 21525641 is a prime.

Together with 21525641, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21525641) 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 as a sum of consecutive naturals, namely, 10762821 + 10762822.

It is an arithmetic number, because the mean of its divisors is an integer number (10762822).

Almost surely, 2^21525643 is an apocalyptic number.

21525643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525643 is an equidigital number, since it uses as much as digits as its factorization.

21525643 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7200, while the sum is 28.

The square root of 21525643 is about 4639.5735795437. The cubic root of 21525643 is about 278.1753935198.

The spelling of 21525643 in words is "twenty-one million, five hundred twenty-five thousand, six hundred forty-three".