21135571 has 4 divisors (see below), whose sum is σ = 21585312. Its totient is φ = 20685832.

The previous prime is 21135559. The next prime is 21135589. The reversal of 21135571 is 17553112.

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 21135571 - 2¹¹ = 21133523 is a prime.

It is a super-2 number, since 2×21135571² = 893424722992082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21135071) 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, 224800 + ... + 224893.

It is an arithmetic number, because the mean of its divisors is an integer number (5396328).

Almost surely, 2^21135571 is an apocalyptic number.

21135571 is a deficient number, since it is larger than the sum of its proper divisors (449741).

21135571 is an equidigital number, since it uses as much as digits as its factorization.

21135571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 449740.

The product of its digits is 1050, while the sum is 25.

The square root of 21135571 is about 4597.3439070837. The cubic root of 21135571 is about 276.4848431949.

Adding to 21135571 its reverse (17553112), we get a palindrome (38688683).

The spelling of 21135571 in words is "twenty-one million, one hundred thirty-five thousand, five hundred seventy-one".