21268559 has 4 divisors (see below), whose sum is σ = 22904616. Its totient is φ = 19632504.

The previous prime is 21268553. The next prime is 21268567. The reversal of 21268559 is 95586212.

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 21268559 - 2¹⁶ = 21203023 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 (21268553) 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, 818009 + ... + 818034.

It is an arithmetic number, because the mean of its divisors is an integer number (5726154).

Almost surely, 2^21268559 is an apocalyptic number.

21268559 is a deficient number, since it is larger than the sum of its proper divisors (1636057).

21268559 is a wasteful number, since it uses less digits than its factorization.

21268559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1636056.

The product of its digits is 43200, while the sum is 38.

The square root of 21268559 is about 4611.7847954995. The cubic root of 21268559 is about 277.0635250744.

The spelling of 21268559 in words is "twenty-one million, two hundred sixty-eight thousand, five hundred fifty-nine".