21266543 has 4 divisors (see below), whose sum is σ = 21359640. Its totient is φ = 21173448.

The previous prime is 21266521. The next prime is 21266551. The reversal of 21266543 is 34566212.

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 21266543 - 2²² = 17072239 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 (21266503) 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, 46205 + ... + 46662.

It is an arithmetic number, because the mean of its divisors is an integer number (5339910).

Almost surely, 2^21266543 is an apocalyptic number.

21266543 is a deficient number, since it is larger than the sum of its proper divisors (93097).

21266543 is an equidigital number, since it uses as much as digits as its factorization.

21266543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93096.

The product of its digits is 8640, while the sum is 29.

The square root of 21266543 is about 4611.5662198433. The cubic root of 21266543 is about 277.0547707167.

The spelling of 21266543 in words is "twenty-one million, two hundred sixty-six thousand, five hundred forty-three".