21523559 has 4 divisors (see below), whose sum is σ = 21536904. Its totient is φ = 21510216.

The previous prime is 21523543. The next prime is 21523571. The reversal of 21523559 is 95532512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21523559 - 2⁴ = 21523543 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523519) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3857 + ... + 7610.

It is an arithmetic number, because the mean of its divisors is an integer number (5384226).

Almost surely, 2^21523559 is an apocalyptic number.

21523559 is a deficient number, since it is larger than the sum of its proper divisors (13345).

21523559 is a wasteful number, since it uses less digits than its factorization.

21523559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13344.

The product of its digits is 13500, while the sum is 32.

The square root of 21523559 is about 4639.3489845020. The cubic root of 21523559 is about 278.1664160686.

The spelling of 21523559 in words is "twenty-one million, five hundred twenty-three thousand, five hundred fifty-nine".