21523605 has 16 divisors (see below), whose sum is σ = 34781184. Its totient is φ = 11364800.

The previous prime is 21523591. The next prime is 21523609. The reversal of 21523605 is 50632512.

It is not a de Polignac number, because 21523605 - 2⁴ = 21523589 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523609) 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 15 ways as a sum of consecutive naturals, for example, 5589 + ... + 8618.

It is an arithmetic number, because the mean of its divisors is an integer number (2173824).

Almost surely, 2^21523605 is an apocalyptic number.

It is an amenable number.

21523605 is a deficient number, since it is larger than the sum of its proper divisors (13257579).

21523605 is a wasteful number, since it uses less digits than its factorization.

21523605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14316.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21523605 is about 4639.3539420915. The cubic root of 21523605 is about 278.1666142336.

It can be divided in two parts, 21 and 523605, that multiplied together give a triangular number (10995705 = T₄₆₈₉).

The spelling of 21523605 in words is "twenty-one million, five hundred twenty-three thousand, six hundred five".