21006571 has 4 divisors (see below), whose sum is σ = 22112200. Its totient is φ = 19900944.

The previous prime is 21006563. The next prime is 21006593. The reversal of 21006571 is 17560012.

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 21006571 - 2³ = 21006563 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21006511) 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, 552786 + ... + 552823.

It is an arithmetic number, because the mean of its divisors is an integer number (5528050).

Almost surely, 2^21006571 is an apocalyptic number.

21006571 is a deficient number, since it is larger than the sum of its proper divisors (1105629).

21006571 is a wasteful number, since it uses less digits than its factorization.

21006571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1105628.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 21006571 is about 4583.2925937583. The cubic root of 21006571 is about 275.9211906543.

Adding to 21006571 its reverse (17560012), we get a palindrome (38566583).

The spelling of 21006571 in words is "twenty-one million, six thousand, five hundred seventy-one".