21534571 has 4 divisors (see below), whose sum is σ = 21586144. Its totient is φ = 21483000.

The previous prime is 21534551. The next prime is 21534577. The reversal of 21534571 is 17543512.

It is a happy number.

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 21534571 - 2²³ = 13145963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21534577) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25155 + ... + 25996.

It is an arithmetic number, because the mean of its divisors is an integer number (5396536).

Almost surely, 2^21534571 is an apocalyptic number.

21534571 is a deficient number, since it is larger than the sum of its proper divisors (51573).

21534571 is an equidigital number, since it uses as much as digits as its factorization.

21534571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51572.

The product of its digits is 4200, while the sum is 28.

The square root of 21534571 is about 4640.5356371867. The cubic root of 21534571 is about 278.2138469841.

It can be divided in two parts, 2153 and 4571, that added together give a square (6724 = 82²).

The spelling of 21534571 in words is "twenty-one million, five hundred thirty-four thousand, five hundred seventy-one".