21265543 has 4 divisors (see below), whose sum is σ = 22901368. Its totient is φ = 19629720.

The previous prime is 21265537. The next prime is 21265549. The reversal of 21265543 is 34556212.

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

It is an interprime number because it is at equal distance from previous prime (21265537) and next prime (21265549).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21265543 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 (21265549) 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, 817893 + ... + 817918.

It is an arithmetic number, because the mean of its divisors is an integer number (5725342).

Almost surely, 2^21265543 is an apocalyptic number.

21265543 is a deficient number, since it is larger than the sum of its proper divisors (1635825).

21265543 is a wasteful number, since it uses less digits than its factorization.

21265543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1635824.

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

The square root of 21265543 is about 4611.4577955349. The cubic root of 21265543 is about 277.0504280722.

The spelling of 21265543 in words is "twenty-one million, two hundred sixty-five thousand, five hundred forty-three".