21002571 has 20 divisors (see below), whose sum is σ = 31502592. Its totient is φ = 13944528.

The previous prime is 21002567. The next prime is 21002573. The reversal of 21002571 is 17520012.

It is not a de Polignac number, because 21002571 - 2² = 21002567 is a prime.

It is a super-2 number, since 2×21002571² = 882215977220082, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21002573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 30685 + ... + 31361.

Almost surely, 2^21002571 is an apocalyptic number.

21002571 is a deficient number, since it is larger than the sum of its proper divisors (10500021).

21002571 is an equidigital number, since it uses as much as digits as its factorization.

21002571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1072 (or 1063 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21002571 is about 4582.8562054684. The cubic root of 21002571 is about 275.9036762169.

Adding to 21002571 its reverse (17520012), we get a palindrome (38522583).

The spelling of 21002571 in words is "twenty-one million, two thousand, five hundred seventy-one".