21105502571 has 4 divisors (see below), whose sum is σ = 21106218000. Its totient is φ = 21104787144.

The previous prime is 21105502549. The next prime is 21105502573. The reversal of 21105502571 is 17520550112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21105502571 is a prime.

It is a super-2 number, since 2×21105502571² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21105502573) 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, 311471 + ... + 373128.

It is an arithmetic number, because the mean of its divisors is an integer number (5276554500).

Almost surely, 2^21105502571 is an apocalyptic number.

21105502571 is a deficient number, since it is larger than the sum of its proper divisors (715429).

21105502571 is an equidigital number, since it uses as much as digits as its factorization.

21105502571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 715428.

The product of its (nonzero) digits is 3500, while the sum is 29.

The spelling of 21105502571 in words is "twenty-one billion, one hundred five million, five hundred two thousand, five hundred seventy-one".